“most necrotizing skin lesions are not caused by spiders.”
So are you arguing that brown recluse bites can do that?
If so your source of information is incorrect. They can be a nasty nasty bite, fortunately they only inject their venom in about 50% of their bites.
I’m saying that when people show up in the doctor’s office or ER with a necrotic skin lesion, 90% of the time it’s not from a spider, even though they often think it is. ‘Must have bitten me in my sleep.’