When Larsen first released the NMO-150/450/800, it was marketed as a monitor antenna. There was no mention of transmitting, power handling capability, SWR, etc.
After a few years on the market, they changed. It started being marketed as a multiband antenna for multiband radios, probably around the time the first tri-band LMR radios hit the market. It does just fine when used where it's designed. I think it's good up to 100 watts.