I'm bumping this topic because I just went and found all the pirate treasure in the PC version of the game. I intend to do the same for the Switch version, once I get far enough into it. I'm also thinking about completing the game 100% now that I've had some time to cool off from my initial frustrations with the game.
Incidentally, I was wondering if Playtonic could update the "Totals" sub-menu with something that shows you've collected the Pirate Treasures. They did the same thing for Stop 'n Swap back in Banjo-Kazooie, even though they were supposed to be secret, too.
I hope there's a cool pay-off for these things... and I like the idea that there might be an ongoing pirate theme with the Yooka-Laylee series, should their be more games after this. I also like that one fan-theory that V.I.L.E. might actually be a group of pirates. I just think pirates are cool.
For development "Twoka-Laylee", please watch these:
For everyone else, talk about these videos !