I think you misunderstood what beefers said. Open play (non-league / unsanctioned / walk into the center and pay for some games of bowling) for most of us is nothing more than practice, and score doesn't matter in practice. So an extra pin that falls when it should be a gutterball doesn't matter. So there is no need to correct the score to reflect that pin.
Now if you are in open play and competing against someone (or just care about having the exact correct score), then it is up to you whether or not to correct for a pin knocked down by a gutterball. Most recreactional bowlers won't, I would venture to say the vast majority of them don't even know they are supposed to as they have never bowled in a league before.
In league play / tournaments / other sanctioned play, where score counts and rules are in effect, as soon as the ball enters the gutter the ball is out of play, and should it bounce out and hit a pin, that rack should be reset and score set to 0 (for a first ball) or for a second ball the pin count should be removed from the score. That is a set-in-stone USBC rule, and I doubt any league would elect to ignore this rule (not even sure they could).
Before I posted this thread, I looked up whatever I could find online and it clearly stated that some leagues/tournaments etc DO allow the pinfall even on gutterballs, which is why I posted the thread. If I hadnt read this and that all leagues and USBC rules always do NOT allow pinfall scoring on gutterballs, there wouldnt be anything to discuss. Apparently, from what I have read, this rule is NOT always the same, even in some tournaments or leagues. But if the official USBC rule is that gutterballs are always scored as zero, thats fine with me, I agree with the rule. Zero skill, Zero score.
Regarding scoring by the rules, I dont believe it really matters if its a pro, league, or or recreational, there is only one way to score correctly, usbc rules unless the league or tournament states otherwise I would think. Sure if you bowling all by yourself it would not matter, but if you want to have an amateur non league or non tournament match with someone, then there has to be a predetermined and consistant set of rules for scoring. Without that
then determining the winner of a match would be sometimes impossible which would be unacceptable outcome.
I have bowled in leagues and recreationally often, there is no difference for me in desireability of consistant and clear rules of the game. If a league or tournament makes an exception to the rules and it is clear and predetermined, I have no problem with that, but in the absence of something like that, then I would think it is very desireable to use all USBC rules ( including gutterball scoring rules ) as the default for any matches whatsoever (unless its pre-agreed to use any special rules for whatever reason).