No, I wouldn't agree.
My opinion is if you can build a rocket that can handle a G64, building the bigger I-ROC with the naturally required bigger fillets, etc. required for the bigger parts is almost a given that it will hold up to the H550. I would expect the rocket that held up to the G64 would almost certainly hold up to the H550 also.
Over the years I've come to see that most people totally over estimate the loads and forces on cardboard rockets and the required build methods needed to fly on higher power motors.
The only rocket I ever "shreaded" because the motor was too large was one printed out on a sheet of paper and constructed with paper glue. It flew fine on a A8-3, but ripped the fins off when I couldn't resist flying it on a C6-7. The body tube held up fine. Just the fact a paper rocket made totally from a single sheet of printer paper can fly on a A8-3 shows that the structure of most rockets are much stronger than most people give them credit for.
I've flown every one of my 24mm Estes D rockets on composite F24W or F39T motors and everyone had held up fine, including the
Renegade D with its side tubes and fin pods. I think most of us underestimate the strength and durability of cardboard rockets.