The FabKit is magical
The laser head is made from 1mm stainless steel Did you engrave this without any coating?
I’m not sure why, It may be the grade of stainless or there is a protective coating or substance which makes lasering easier for production is still present so even the FabKits 40W laser is able to etch it.
Both the bed frame for the honey comb and the laser head are laser cut from the same stainless steel.
You will notice your laser bed frame has likey got lots of lines etc engraved on it from cutting jobs.
I might order some more stainless just to test more engravings and see why it is.