Unless you have observed all users then you are pulling the "people lost data" out of thin air.
Here is something that actually happens since version 2.8: if you do not treat XCF files as the master image file format, GIMP complains all the time.
Re:Gimp 2.10.12
by prokoudine on Friday June 14, 2019 @10:47AM
(#20183434)
Oh yeah, I've been pulling that "out of thin air" for, ugh, 7 years now. That's 7 years of actual user support, every day.
I'd like to see you prove me wrong.
GIMP since version 2.8: only allow exporting to JPG/PNG/TIFF etc., warn if data wasn't saved. Actual results: only a few cases of lost data.
We did the math. Now you do yours :)