Thanks, ChatGPT helped identify this issue (after 4 rounds).
I do all my raw editing using Bridge/ACR, but then import all into LR for browsing and filtering. I imported a recent large batch of ACR edited images, went to LR to review, and noticed none of my ACR edits appeared in the Library module thumbs or previews. Lots of cropping, removals, Denoise AI. But, if I went into the Develop module, the ACR edits were all there and the preview was correct.
ChatGPT asked me to use the Library/Previews command to re-generate standard or full sized previews. Did that, and Volia, the Library previews were now all correct, reflecting all the edits in xmp/acr sidecars. ChatGPT declared it a bug in the import preview generation.
I'm on Windows 23H2, new Photoshop V27 and ACR V18. I'm curious why others don't see this. Is there some LR import preference I'm missing? Like a way to force Standard or full sized previews on import?