A Beta will be good because I know a lot of classic die hards will want everything in game to be perfect and even Blizzard said they wanna hear from the community. So having them test it out will be for the better.
I love Warcraft, I dislike WoW
Unsubbed since January 2021, now a Warcraft fan from a distance
Nost wasn't really Blizzlike at all, even their dev's said so in various interviews. A lot of backend data was guesswork. They tried to be as Blizzlike as they could be, you have to give them that, but something being the way it is on a private server doesn't mean it was like that in Vanilla. Due to that you don't really want to have private server players report "bugs" of give feedback because it was like that on Nost or whatever other pserver. You wan't ppl to report stuff with evidence bases off actual Vanilla servers, and for some stuff there won't be any evidence that can be validated. Only Blizzard can Validate that stuff from their own sourcecode and databases.
Which is why I say none of these people who had played on those servers have ever been playing Vanilla. Just a crude replica by people looking to make money off donations and gold/item sales before vanishing in the night.
On topic: An open beta a month or two before launch to make sure all the kinks are worked out is very likely. It's not like they are releasing an expansion, so there shouldn't be a need for as much feedback or testing as there usually is meaning a closed beta should be skipped.
Open beta so we can test addons.
Which I replied to further in my comment. Got to love when people only read 1/6 of the paragraph. I mentioned blizzcon because they explicitly stated why a beta will be necessary, thus also implying the format of open beta. The more people testing, the more areas are tested.