Yeah I got a Pinephone for this exact peripheral and it doesn't even correctly fit the size of the phone. Not universal for all their phones so beware.
How did yours not fit? The body of the OG and Pro Pinephones are the exact same, it's only the internals that are different. I literally use the back cover from my OG Pinephone for my Pro, and am hanging onto my dead Pinephone for spare parts, should I ever break the screen on my Pro.
My keyboard accessory fits both of my PinePhones and my PinePhone Pro - it's not easy to put it in or out, but that makes it stay in and not fall out accidentaly.
That said, in mine the accesories battery no longer charges, so there are definitely issues with the keyboard accessory aside from being humongous.
[0] https://pine64.com/product/pinephone-pinephone-pro-keyboard-...