I’ve done probably 70-80 keys so far and have never seen anyone ask anyone what their spec was lol.
Fistweaving IS the meta mythic+ build by the way, so even if this actually happened (doubtful) maybe you dodged a bullet not grouping with them.
Also, there is some nuance in knowing when you need to actually do some casted healing instead of just spamming damage. Being a “fistweaver” doesn’t mean you only heal through dps.