Tashigi said that all the famous swordsmen are either pirates or bounty hunters. This means that bounty hunters have to have been a significant force in OP. But where are they now?
So far we haven't seen any strong bounty hunters, save for Zoro. So what's up with Tashigi's statement? Did Oda change his mind/forget? I think not.
I think its very likely that Fujitora and Greenbull, as well as other strong new marines recruited via the draft, are former bounty hunters. Fuji and GB both have swords, so it would fit Tashigi's statement of there being famous bounty hunting swordsmen. It would also explain how two top tiers seemingly appeared out of nowhere. These guys were already strong bounty hunters active in the NW until the WG bought them over and made them admirals.
If they are bounty hunters, I think its very likely that their swords are extremely rare. imo they at least have a great grade but supreme grade isn't off the table. Given how there are 12 supreme grade swords, I don't know how exclusive Oda will keep them going forward.