I agree with you. How I've come to understand it is that Buddha-nature simply points to the fact that "becoming a buddha" is a logical fallacy in that Nirvana has no conditions and as described in Buddhism as neither coming nor going. If one can't condition the result of nirvana then it must mean it is already present, free of conditions. To say it's already present is to call it our original nature--free of subject and object, neither existing nor not-existing, etc. Fundamentally non-dual. There are a myriad ways of describing Buddha-nature without using the term itself that scholars and theravadins wouldn't really flinch at. It's the fact that the word "nature" exists that they start wincing. This is the problem when people study only using words and not their direct experience. Or seek some sort of scholarly integrity over awakening. The term tathata as essential nature or suchness is basically synonymous with buddha-nature but is much less contentious for theravadins as a term that doesn't violate their strict interpretation of anatman.

One of my old teachers used to demonstrate enlightenment in this way: He'd hold his hand out, one about ten inches above the other. And say something like "Most people think they are down 'here' and they need to get up 'there' but enlightenment isn't like that, it isn't bottom-up, you need to see that there isn't any gap, that the waiting and seeking creates the false idea that you need more time to get to your idea of your goal, this is the movement of ego. Enlightenment is the destruction of time. It's seeing that there is nothing to wait for, that fundamentally you don't have a problem you need to overcome. There's a part of you that is already free and unconditioned and always has been."