As above, theoretically it voids the warranty and it may well handle a bit worse on climbs. Having said that, I’m running 140mm forks with 10mm of lower headset. The front end gets wandery on really steep stuff but it’s very manageable (I’m not the kind of person to get off and push…). I could have used a zero-stack headset which would have put the front end 10mm lower or allowed a 150mm fork with the same front end height / head angle. The ‘trouble’ with the ASR-5 is that whilst it’s a very lightweight frame, its geometry encourages you you to rag it. So I think 150mm could be a lot of fun but I can understand why Yeti may not want people running such big forks and ragging it that hard.
The other thing to consider is the axle-crown length of various forks. E.g. a 140mm rockshox rev has a bigger A-to-C than a 140mm Marz 44 IIRC.
200mm discs on an XC bike? Yeah, that’s dumb.