Agreed, I had the exact same situation with string bends - I decided I can bend them without the proper support like it is taught here, until I read that this can lead to the loss of the fingernail if the string comes back under the nail. It's always best to give the technique they are teaching a fair try at the very least. Though I have to admit my thumb moves all over the place when I'm playing, but I do use it to hold the 6th string every now and again, e.g. on the root 6 minor 9 chord, so that's probably why.