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It makes no sense of course, it shouldn't matter if the default library is huge, there is no reason whatesoever to read through the whole library at startup and put any information into memory, other than a single listing of file folders/files in one directory for the list you would see in this window on startup.

As I said, it does need to do that for the library dropdown menu... That triangle thingy on top of the content you're seeing for the current library directory you're in, that allows to navigate through the entire library structure without clicking up and down through the library. So as I said, if you don't use it, set the timeout so low that it doesn't bother reading the library for too long.