Depends on what you mean by corroborated. I mean, it would be interesting to do a point by point comparison between this and the Dassey confessions, but frankly, I doubt it is worth the time.
But there are definitely some things that don't add up.
For example, he left out the hair cutting (unless I missed it). While this seems like a silly thing a silly boy made up, if it really DID happen, that would be a fairly significant thing. Steven probably wouldn't have done it in order to fulfill his lifelong dream of being a barber. Cutting a woman's hair has been a way to humiliate and embarrass women historically. A way to mutilate them and damage their sense of self.
These are pretty sad to look at, but no gore or anything like that.
http://rarehistoricalphotos.com/french-female-collaborator-punished-head-shaved-publicly-mark-1944/
Maybe he didn't know this type of history.
But it isn't a major leap to think a murderous rapist would think "I'm gonna make this ***** ugly" and cut her hair. Other killers have done hair cutting.
Forcible hair cutting has occurred in Amish communities as well as forcible beard cutting.
If they cut Teresa's hair, then that would probably be a thing Steven would brag about- debasing her like that. It is a real controlling nutjob thing to do. Weird the prosecution didn't obsess over it and Evans didn't mention it. And we "know" that it happened as much as we "know" pretty much anything in the Dassey confessions happened.
Other things in this category include saying Steven used his shirt and socks to tie her, when we "know" he used those sex shop handcuffs. Or that Avery twice in the head, twice in the chest and once in the vagina. When we "know" that he shot her 11 times total.
Then there is the "he cut her throat, but not much" aspect, which is just funny. It seems pretty apparent that this is stupid nonsense.
The "stuff only a killer would know" is exactly that, stuff only the killer would know and we literally have no way of gauging how accurate this is and as a result is worthless unless Steven confesses or admits to telling this guy stuff.
What can we corroborate with the evidence?.... Well Teresa is dead. So score one for Evans.