The parts -> thickness tool doesn't work at all with booleans or constantly locks up.  The only way to make hollow solids is sketching a cross section & revolving/lofting with solid mode enabled.

A big problem seems to be its reliance on interpreted python routines for inner loops.  When you apply a part tool, it calls a python routine in that tool for thousands of vertices.  As the models get more complex, it gets slower & slower just so the guy who wrote it can pass a job interview.

You can cut & paste models between different fcstd files. It's much easier to create sections in different files & combine them later than to do the complete model in a single file.

The lion kingdom is fully aware whatever model it creates is going to be completely worthless when the next BFR redesign comes around.  It's manely about discovering the tools.