Classic (pre-2001) Mac OS used "suitcase" font files, where TrueType font data was stored in the file's resource fork instead of the data fork. Wine has support for converting suitcases into individual .ttf files that Windows apps could directly open, possibly driven by Mac OS X 10.4 shipping the Microsoft core web fonts as suitcases. Remove this support, it uses very deprecated APIs and suitcase font files are largely history (although macOS can still use them).
CrossOver has disabled this functionality since 2018 (because of an FSRef-related bug in macOS 10.13), without any customer complains that I'm aware of.