The telling part about uselessness of that window is that the most visible difference between StarOffice 5.2 and OpenOffice.org 1.0 was that equivalent of this window was removed. It got reintroduced probably because it makes packaging LibreOffice for macOS easier.

While it may not be essential for experienced users, I think it is very important for beginners.

Imagine you know nothing about LibreOffice, except that it is an office suite. You download the thing, install it and now what? Most people expect to have something called "LibreOffice" that can be launched and does something sensible. That's what the start page is for.

It is also the reason why it is a good spot for a fundraiser. It tells new users that LibreOffice takes donations, but it will not get in the way of experienced users who already know how LibreOffice work as they are likely to skip the start page entirely.