Demondoink
I think you kind of underestimating here how wide we should continue in those BVB limp-check spots
I think we should continue pretty much every hand with BD straight and 2 overs to the 8 vs the flop raise, and almost every BD flush hand. so we do arrive on the river with a bunch of 9/T/J highs or even some worse, and not only suited combos but even some T9o 79o JTo type hands, alongside a bunch of 67s and Q4s type hands
so I think we are not deficient in bluffs at all, and should probably even give up some high card combos

i guess it could be that i am used to playing limp ranges in cash games where my range is much tighter, as opposed to a range that contains close to 100% of hands. however i do realise how wide you are supposed to be continuing in these kind of spots, as players similarly over fold in srp's btn vs bb when you look at some of the flop continues that PIO manages to pull off.

i am still a little dubious whether people actually call the hands you mentioned vs flop raise. of course the K highs and two overs etc i would expect to continue, but not to bluff otr on this line. and then some of the hands you mentioned will be mixing between call/fold in equilibrium, but in actual play i very rarely see these combos actually calling either from watching Elite level mtt content on here, or from whenever i play an mtt and reach showdown on a similar line (albeit i am not playing $25ks when i play a tournament haha). also some of these air combos will be distributed towards the x fold line, so you can further reduce their weight to arrive otr.

i would imagine PIO easily finds enough bluffs here, but i'm sceptical whether players actually find these continues on early streets that allow them to have a high enough bluffing frequency otr. could easily be wrong, though. i mean JTo/T9o for example is already 32 combos, and given the fact that there are two Ax on the board reduces the trips in both ranges to where if we bluffed both of these combos we may already be over bluffing.

so perhaps i am talking myself out of my original assumptions haha. though i dunno whether Q/J highs always wanna bluff otr as they have some EV as a x down vs the pure air raising portion of IP. prob just wanna mix them i guess.

Demondoink
I agree that overall ''population'' will be just over foldy in pretty much every node in this spot, but Seth is not population and this tournament has more competitive field in it. I'm sure Seth won't be hugely overfolding flop or something, worst case he will overfold a little bit (especially if expecting BB to be too passive)
I agree with what you convinced yourself (:
I think it's actually pretty easy to overbluff the spot if you start taking too many J/Q high's and bluff'em
because I also tend to think population will play this sort of spots too aggressively OTF OOP, so it's reasonable to assume it will even out with under floating vs the flop raise

not sure if Q high will ever want to bluff there TBH, maybe some Q2/Q4 having good blockers for rivered straights and the most freq checked back Axs from BB, could be good candidates for the overbet sizing