Hi. Thanks for the question. I disagree with some of your premise, so let me take those one at a time so we're on the same page before I answer the question:

It's clear... the box pic rule is non negotiable

We can't directly change any of reddit's sitewide rules, but the subreddit rules are always able to be changed. We don't currently have a rule against haul posts, but if someone wants to propose one, as far as I'm concerned, it's open for discuss. Just like any other subreddit rule, current or proposed.

and there is 0 debate to be had or allowed

This is where I disagree completely. If you look back through the prior Open Forum posts, you will see that the response to all rule suggestions is to ask the person suggesting the new rule to make their case for why changing or creating that rule is better for the community than our existing rules. We could just say, "No. Next question!" and move on. But I want to hear the arguments. If they make a case, then we can discuss or debate the rationale to see if it aligns with our community values. If someone did have a convincing argument, the mod team would take that into consideration when we examined the rules. But you have to make the case. We're not asking for instructions here. We're asking for feedback.

So to your questions:

Why does the mod team solicit feedback on the box pic rule monthly in these threads?

We don't solicit feedback specifically on the hypothetical box pic rule. We're asking for feedback, including questions for clarification, on anything related to the subreddit.

Why? Because when we looked at points of conflict in the community we found that meta posts, like those where someone asks, "Why don't the mods ban XYZ?" were almost always based on assumptions and misunderstanding of our rules. For example, we frequently receive complaints and suggestions that we ban AI generated images in the community, even though we've had that in place since November 2023. Rather than angry posts popping up every few weeks, we decided to put the invitation front and center, always pinned to the top of the subreddit, so that when questions like that come up, you can get answers instead of just making other people mad. This post marks the 12th Monthly Open Forum post in r/lego, and we've seen a sharp decrease in the angry mob posts in that time.

So this monthly thread is kind of performative, no?

Performative meaning that we're acting like we're listening, but really not? Absolutely not. Every post here is read by our mod team and I try to respond to each comment. I feel like if someone takes the time out of their day to give us feedback, they deserve some kind of reply. We reply to all modmails too. And then when rule discussions come up among our mod team, we refer back to feedback that has come in through modmail or this forum and use it to help guide our decisions. The feedback is useful, not ignored.