The only requirement for core is that it is loaded before the maker specific plugin in the load order (ie: the Ramza_CraftingSystem plugin). You should also update that plugin as well, if you haven't already, if the version you were previously using was old enough that it didn't require the core plugin, you're working with a version that had several bugs in it that have been fixed, at the very least. There had been an apparently long standing bug where the function I described above simply caused a crash.
With that being said, I loaded up my test project after some hilarious cloud based backup shenanigans on my new laptop, and managed to confirm that using the function above does grant experience to the specific crafting category, and caused it to level up, and reset the rollover experience as I expected it would, in both MV and MZ versions.
I would definitely recommend updating the crafting system plugin for sure, since you weren't previously using the core plugin, your older version is likely woefully out of date, and that function not doing what it's supposed to is likely the least of your problems.
~Ramza