yeah, apparently. Had a quick peek at tagcache.c which seems a bit daunting at first glance.
For my personal usage, I think I will leave the directory cache disabled as I only ever use the database. Wasn't really aware that it had been enabled in the first place. I also just realized that either loading the DB to RAM or building the dir cache each, individually, just takes a few seconds after booting, but having both enabled at the same time results in a ~40 second waiting time during which the database is extremely slow to use. This means that turning off the dir cache hugely improves the user experience in my case and is something I should have done much earlier.