What is unreasonable about this? Is it not reasonable for an armoured person to be hidden in cover in ambush? As long as they are not moving.
It does make Pass without trace more valuable as now it is highly the group will succeed in the basic hide DC but the Detection DC for some party members could still be low. So, moving into ambush with a fighter/paladin is viable but not guaranteed and there is still a reasonable chance that the fighter will be detected by the NPC but the stealthy guys will still get surprise.
I'll provide an illustrative example of what seems to be the playtest's RAW right now.
Bob the fighter is wearing plate, has no stealth prof, and has 8 dex. His Dex (stealth) checks are rolled at -1 and disadvantage.
DM: You stand near the cave's entrance. Are you going to enter?
Bob: Wait, before we go, I crouch behind a rock and attempt to become hidden.
DM: Roll a Dex check.
Bob: I have -1, and disadvantage - rolls - highest roll is 4.
DM: You are not hidden.
Bob: Ok, trying again next round, we can spare a minute.
DM: Roll again.
Bob: -rolls- oh, a natural 1!
DM: Clearly you're not hidden, but you get inspiration, I guess?
Bob: Trying again! -rolls- Another natural 1!
DM: According to the rules, you can give inspiration to another party member.
and so on...
Obviously, no DM would allow this to happen, some kind of ruling would be made on the spot to avoid abuse, but it looks like this is the playtest's RAW. It should be fixed.