Basically this seems to be the most important point OP has to say. If someone isn't valuebetting thin enough(and since he said jamming, I think that he is talking specifically about the river), there's these implications in their strategy:

1-They're overbluffing, because they expect their bets to get more folds, so the natural adjustment would be to keep bluffing while not valuebetting as thin, leaving their river shoving range quite air-heavy.

2-They understand they're not valuebetting so much, so they don't bluff as much, they keep valuebetting a very strong range, missing thin valuebets and not overbluffing, which in practice would look more like a nutty range. The problem of doing this is that those regs don't apply enough pressure to villain's equity, letting them realize a ton of equity.

Vs player type 1, the solution is to call the river a ton of the time after calling the turn to get money from his bluffs.

Vs player type 2, the solution is to call most turns planning on folding rivers. The good thing about that approach is that hero will be able to cooler player type 2 when he has a valuebet and even if his weak holdings don't get there, there's a chance that they will win at showdown from villain's give ups.

Now this is the next type of exploit the pool CRAIbaby is giving to us, which came from this:

Basically this leaves us to player type 3, which is super common in the lower stakes, which is a guy that "pot controls" a ton, a reg that uses the bet-check-bet line a ton, he is basically a bigger nit than player type 2. This is the type of guy that bet AK in a 3-bet pot in a board like A44r, checks a blank turn and bets river. These guys do stuff like that to induce bluffs/underrep their hands and get calls from worse more often.

vs this type of guy we get even more free equity and coolering potential vs them, by making plays like call 3-bet, check-call flop, check turn and range checking OTR, we can get his stack if we bink something. This kind of villain could also overbluff turns, since they check back a ton with their valuebets. So lead-bluffing them OTR is quite bad, just check-fold most stuff and check-raise anything that has value to do so.

I think CRAIbaby is giving us hints about exploiting those tendencies and that they're common in 500z.

I don't know if it's that true, those leaks seem more like leaks from microstakes regs and 100z regs.