Originally posted by jonnin:

if you are absolutely sure something reverted, you may need to verify that you didn't lose things in your home or chests etc as it could be that your world reverted.

Oh, not at all that. Just a handful of birch trees were mixed in with the trees I had planted in an area which I thought I cleared. There could have been tiny (not fully grown yet) birch trees that I missed.
Nothing else changed, and I've been actively building and decorating in my base every day, so a reversion would be pretty noticeable. I'm quite sure that it didn't happen.

Thank you all for your responses. I do not WANT trees to respawn without me planting them intentionally, to be clear. So I'm glad to find that the answer is still "no, they do not".