You're right and I was misremembering (we had only developed against modern mobile browsers), though I am 100% certain we made use of these extensions on iOS Safari, so I honestly don't believe caniuse when they assert that it supports _neither_ extension. Per my recollection, iOS Safari supported the large blob extension quite early on.
Apologies for the brash statement earlier; that was wrong of me.
Apologies for the brash statement earlier; that was wrong of me.