they don't, which is why they ask in the first place. I never said they could just use it at will, I said I do not need an in-depth review, but would instead do a quick look over.without a review how do you know it is a "bigger" 3pps? heck, how does the player know what you consider 'bigger' without telling you and showing you??
As to bigger 3pp, it has the name of the publisher and/or author on it, so for some that might already be all it takes to allow it (with the caveat of addressing things as they pop up - but that is true for WotC material as well...), others need a quick glance. We are not talking hours here, so the 'I do not have time to review three classes' feels a bit odd to me (but then my game is more 'loose' anyway and not tight tactical where it might matter more)
What I am generally not doing is reviewing e.g. all Warlords and saying 'use this one', that is more work, I am just saying yay or nay for the one. If this comes up early enough in advance though, then even that is an option, as my review is not going to be so detailed that it takes so long.now remember there are atleast 4 warlords on DMsguild... so If I am the DM and Ross brings me 1, and I don;t like it, I used to just go look for 1 I did and say "how about this?" I don't have the time to look them all over.