You're missing the whole point of my post which is that all class 10 cards are NOT created equal. Most have good read speeds but most budget cards have crap write speeds and will not give the best most reliable performance. People need to check the write speed specs of any card before they consider purchase.
@BenDronePilot you didn't click the link or read the standard, did you?
Class 10 is a standard of write speed, a class 10 card must be able to sustain 10MB/s sequential write. Read speed is irrelevant for Class 10 (or UHS-1 or UHS-3).
The P3 encodes 4K and UHD video at 7.5MB/s (60mbps), therefore any legitimate Class 10 card will work fine.