The problem with the big trackers isn't that they're prudish. It's that they're imprecise. 'Spicy' is one checkbox covering sweet heat, slow burn payoff, dark, taboo, monster romance and everything in between — which means it tells you nothing.
So readers build workarounds. A spreadsheet with a flames column. A Notes app entry at 2am. A Notion template abandoned after a fortnight. Three systems, none of which talk to each other, all of which you maintain by hand.
What a spice-first tracker does differently is treat intensity, flavour, tropes and content notes as four independent layers on the same book. A five-star book can be one flame. A two-star book can be five. Neither of those is a contradiction.
That's what Forbidden Folio is: your shelf, cover-forward, with the vocabulary you already use and no hierarchy of kink. The spreadsheet can retire.
For the vocabulary itself — flavour by flavour — The Scarlet Pages keeps a lexicon of dark romance tropes.