Indesign 20.2, Windows 11
Not sure if this can be reproduced, but here is what I did:
1. Created an INDD with two pages with size 180x264, no margins
2. At the bottom of the second page placed a text frame with some text, so its bottom-left corner is at X=0 and Y=264
3. Saved the INDD and placed it another INDD
4. When applying "Fit frame to content" on the placed object, the displayed size changed to 180 mm x 260.2 mm

It turns out that the text frame at the bottom of the second page has a different position now. It's sort of shifted by 3.8 mm