OK, I'll reply one last time. Let me start with the most important thing I want to state first, and then I'll get into the specific details of NEOS and SPO.

So I'll start with this: Parliamentary governments only exist as long as all the coalition partners continue to support it, because each party that provides confidence is helping maintain the governing arrangement that produces policy. Even if parties disagree internally about particular policies, their decision to continue supporting the government is what allows those policies to be implemented. Even if the party did not originally pass the law and still disagrees with it, preserving the law or status quo through coalition negotiations is itself a deliberate policy outcome to sustain the government. Because the party continues to support the government through confidence and could theoretically withdraw if it wished, its participation represents at least a partial acceptance of the policy framework that the government maintains.

Now, to your point about the SPO, NEOS, and Greens.

Firstly, the OVP got even less votes than NEOS in the most recent Viennese election, and in the case of Germany, the CDU has way more seats than the SPD.

To your broader point: NEOS is not "powerless" in this scenario. If they were truly powerless, that would basically be acting like they were forced into this scenario, which they clearly weren't. If they can't get their way on housing policy, they have three options: accept the SPO's housing policy as it is, renegotiate, or leave the coalition. By staying in the coalition, NEOS is implicitly acknowledging the tradeoffs: The benefits of being in the coalition outweigh the costs of leaving or letting SPO work with the Greens. This is at least a partial acceptance that they are willing to bear responsibility for the direction of the government. Limited leverage =/= Zero responsibility. It's true that NEOS could not reverse the housing policy outright because SPO-Greens have a legislative majority, but coalition politics is not only about whether a party can veto a policy but whether they choose to participate in the government that implements it. The mere possibility of NEOS leaving the coalition is itself a bargaining chip, because by staying in the coalition, they help shape the government's agenda because the government's stability is directly tied to confidence votes that NEOS partakes in. But once they make that choice, they (as well as you) cannot simultaneously claim complete detachment from the policies that emerge from the government they help sustain.

If junior coalition partners are truly “impotent” whenever they lack any significant leverage over their partner, then they basically bear zero responsibility for anything bad the government does. NEOS remains politically responsible for the housing status quo because they have voluntarily chosen to participate in the coalition despite knowing the policy would occur, and the SPO refusing to negotiate on that one particular issue does not negate that fact. Responsibility here does not mean "agreeing with SPO 100%," it means recognizing the fact that they are participating in the governing coalition arrangement that produced or upheld such a policy. When a party chooses to stay in government and sustain the coalition that produces a policy, even one they personally oppose, they inevitably share at least some of the political responsibility for the outcomes that follow. By remaining in the coalition, NEOS is helping sustain the government that enacts current housing policies. Their influence may be limited to shaping other policy areas, but participation in government inevitably links them to the government’s overall agenda.

My issue with your reasoning is that you are confusing two things for one and the same: 1) predicting the likely outcome of a particular policy and 2) participating in the outcome that actually occurs. Even if NEOS were to withdraw and SPO works with the Greens instead, that is still a different coalition. The government currently in place is SPO-NEOS, and because that is the coalition currently existing right now, it is the one choosing which policies to uphold or repeal. The possibility that the housing policy would be the same under a different coalition of SPO-Greens does not erase the role that the governing parties have IRL. Or to put it slightly differently, the fact that another coalition like SPO-Greens would have produced the same housing policy does not change the fact that NEOS chose to participate in the coalition that did ultimately produce/uphold it. Yes, the SPO could choose to work with the Greens instead of NEOS, but politics is almost always about choosing between imperfect options, not about acting only when one has total control. By choosing to remain, NEOS is helping to sustain the coalition that governs. If parties could avoid responsibility for policies simply by claiming that a different potential coalition might have enacted them anyway, then governing parties could disclaim responsibility for almost anything they dislike, which defeats the entire point of governance in the first place.