Things on last page are smaller

What is smaller? In the last page, there is only one measure (image below) and currently, I don't see difference with the previous page.

I don't see anything that is smaller on the last page than on the previous.
Except the (grand) staff distance, where they don't space wide enough to make room for the melisma undserscores
If you mean that, this is already reported in #280139: Autoplace fails to avoid melisma underscores

and for that spacers are the workaround. As is just removing the system break in the 2nd to last measure, which pulls that last measure over onto the (previously) 2nd to last page