I happen to be an eggsbert on dis topeg :de de de
1. They have a thesaurus of smell notes: floral, citrus, musky, woody, fern-like (*fougere*), oakmossy (aka *chypre*) and probably some others
2. They layer some notes under other notes, creating *accords* of scent
3. De facto, you are right, correct, OP
Perfumers have quite of crisis for new ideas.
However, some brave ideas get through. Expencive "Creed Aventus" pineapple chypre has a frikton of "clones" - other sweet pineapple-like chypre-like scents.
4. Perfume's scent cannot be copyrighted (it counts as "functional property" lol)