I know of one 19ish year old Cat 4 with well north of a 300 watt threshold (he recently did 400 for 20 minutes at ~170 lbs), but he won't be a cat 4 for very long. Or a 3, either.
I'd say a good number of the local cat 1/2s that are 160 lbs+ can do it, but there are also a good number of Cat 2/3s in the 145-165lb range that can't. All the good cat 1s I know can do it easily, and for multiple hours (one did it for four hours a couple of months ago, another just did 325 for 4 hours; pretty big exceptions).
So no, I'd say it is most definitely not common in the least, especially in the lower categories. Easily verifiable on Strava.
But everyone is faster on the internet...