They're full of it...just trying to push their EF-6 which is a massively overpriced and at best very mediocre amplifier imho. I'm typing this with my 6 plugged into the headphone out of my SX-1980 receiver which delivers about 20W into 50 Ohm via the headphone out, currently listening to a C.P.E. Bach concerto on the radio and I can assure you that there are no smoking fragments of drivers flying about. On the contrary, it once again becomes clear how much clean power the HE-6 require to really shine and how they scale up.
BTW: Prep, if you're reading this, I managed to buy F1 boards and other components, love my F5 clone but had the possibility to listen to an F1 and I like its presentation just a hair more though I can imagine it might be a bit too clean/much for some. Whatever you do, don't sell yours (or if you decide to sell, send me a pm first