I have been experiencing this problem for a while now. Basically if I open a multi page PDF in Illustrator and then copy and paste it either into the same document or a different one, it changes from cropping to the bounding box to the bleed box and enlarges it to fill the same area.
I have realised that this is because the last time I placed a pdf file using File/Place I specified cropping to the bleed box in the options.
If I place a file (any file) and specify cropping to Bounding Box, and then open the same multi page PDF as before, the problem does not occur. It appears that by opening a multi page PDF it crops to bounding box but by copying and pasting it reverts to the last used cropping in File/Place and resizes to fit.
This issue is present in both Illustrator 2021 and 2022.
I really think this issue needs sorting by Adobe. Please advise if I should report this somewhere else for attention.