[cowpony]

I plan to hold onto Galen's puppy coat as long as I can, because he'll never be as soft and fluffy again. Once the adult coat and tangling starts, though....zzzzzt. Buh bye floof.

I wonder what your groomer's logic is. I once had a groomer's assistant tell me I would ruin my labradoodle's coat if I trimmed it. That would have made sense if my dog has a double coat, which some doodles do.
However, the "labradoodle" in question was my pure poodle boy Pogo. his parti-phantom markings are unusual for a pure poodle, true, but he's clearly not a double coated dog.