Digital Foundry threads have are troll magnets these days. I'd literally bet my own money most of the people complaining about these XB1 framerate drops wouldn't even notice them if it weren't for the fraps counter in the corner of the screen. Concern trolling of the highest order. People are literally bitter when the XB1 version matches the PS4 version's resolution now.
The game is a solid 60fps the vast majority of the time, and the drops are usually 55ish, and occasionally slightly lower than that. Those are tiny drops that lots of games that are 60 suffer from on occasion.
https://www.youtube.com/watch?v=lvtMXYHasRQ