Don't forget; I'm the one who suggested Risu could sometimes have a bad day with her old text, purely for flavor. I'm completely on board with giving the world more flavor and I love things like washing off the Jammer Beta acid. Which despite doing only 1 acid damage is, hilariously, a much bigger threat than firesplitters will ever be outside of Stylish, purely for the damage to your weapon. Yeah, firesplitters are THAT non-threatening.
The major difference in using the Lava Slime as justification is that Firesplitters are literally zero threat (outside of Stylish, as mentioned, which everyone but me avoids because "it takes too long" and I avoid because of the firesplitters, actually) to anyone with the common sense to hit and run, just like Legumes. (Coincidentally, these also had a thread to neuter them not that long ago.) While, on the flipside, the Lava Slime doesn't even need to attack anyone to kill them if they use melee basics. I've seen a dagger dancing Kensei/VA go down in one round just to the retaliation damage. Disabling this makes much more sense.
Now. Would I COMPLAIN if this was added? Probably not, outside of MAYBE some (hopefully) comedic grumbling about how idiot kids these days can't even move their legs. My opposition to this stems mostly from the fact that Dev's time would be better spent being put towards fixing all the bugs not found in beta because everyone was too busy smashing one anothers' faces in to actually test anything else.
(That, and, you don't want one damage type to completely invalidate an entire classification of monster - especially when that monster literally only has one threat outside of the boss - The Wings of Fire - and even the boss is a non-threat to non-melee characters. One could also argue forgeries against akimbo gunners, to which I say "Fortune Wind. Stop being dumb and attacking with the guns."