Funny review that.
I would recommend reading the manual first and than compare.
So Z would have known that on G109 there are 3 different gain settings,
that the figures for the output power are per channel,
that provisions are made so amp will not explode.
But, if you connect a very sensitive headphone to one socket and a very hard to drive headphone to the other ...
than listen to the hard to drive headphone with high levels ... it may be that you will cook the high sensitive headphone meanwhile ...
Sorry, our gear is not dummy-proof under any circumstances.
Remembers me of the cat in the microwave, the Starbucks labeling on the coffee mug: hot beverage,
and, best of all: Objects in the rear view mirror may be closer than they appear.
There is always a gaggle of attorneys hunting you when you are a manufacturer.
Well, to come back to the point again:
We´ve employed high efficient current limiters and other measures to avoid "explosions" or "flames".
Everything on the "life" side of our gear, power socket, cables, fuse, transformer, power switch, PCB, is made to UL specifications.
Like every responsible manufacturer will do.
https://www.ul.com/
With heavy improper use it may be that something will break inside - but for those cases we have a fuse to cut mains.
Best regards, Fried Reim