I'll tell anyone who will listen not to buy a car thats been developed on a new platform for at least 3 years to give them time to find faults in the design in real world conditions. If your playtesting or in early access you are literally playing a prototype, a bunch of content creators spouting off about how its a buggy mess could put a stink on the whole project that people will remember even if its perfectly polished by launch.
Playtests typically involves a full on NDA for this reason. If your playtest is aimed at creators that are allowed to stream it's not a playtest, it's a marketing exercise.
If its ready to play, just release it, what's the point of a playtest if not to test it. Yeah there's the publicity too, but are we going to pretend that it can't do both.
Employees do testing, already covered by an NDA. Content creators do publicity. If they are restricted to no negative publicity, then they are not reliable and it’s dishonest.
While I agree in principle you will never catch 100% of the bugs pre-launch, has there ever been a game that didnt need at least a few patches in the last 20 years?
Id be keen to read the exact wording of the clause "Dont say anything negative" and "dont say anything negative without talking to us first" are very different statements. I can understand the devs wanting a chance to say "Yep, we know about that and it will be fixed pre-launch" or "Ill put in a ticket to get that looked at ASAP" to the playtesters before they trash the game publicly.
So, even at full release, there could be bugs. That makes the suppression of actual opinions worse. If people didn’t call out unfinished projects, they would not get fixed. If they want preorders, stop making buggy mess games.