Hi, disclaimer, I work at Google, but on parts of the Ads system and not YouTube and not the part of Ads that deals with YouTube (nor am I in management or privy to product launch decision making, quite removed from that part of the org actually).
From random lunch conversations, back when we had them, the throttling behavior you’re describing is certainly technically and from an infrastructure perspective possible, but I’m doubtful it’s desired. Your account might be a part of some private experiment that changes something for you on some browser… just by virtue of your account id hash mod 1000 equalling some random const number, you might be a part of the browser experiment. Usually we’d try to launch things in the other direction, ie. to maximize the bandwidth going to/from you (regardless of revenue). It could be an experiment going wrong that nobody has looked at, given how it’s Christmas and the engineer working on it is away or something… (yes there’s supposed to be automated systems to ramp these experiments down… sometimes they are just broken somehow annoyingly and person changing stuff might regrettably overlook stuff, and/or overly rely on these).
As for reality tv style videos vs. educational content… it’s sad that those reality videos may end up available in higher quality because they’re served from a more nearby cache to people watching those (BBR and quic/http3 and random technical reasons like that) - whereas what I (and probably you as well) consider smart contents tends to be served from “core network” datacenter further away, making it more suceptible to random stuff happening on the internet.
The Google internal network capacity that would be used to deliver these niche videos from core network to a pop nearest to your ISPs advertised route is usually not a problem, and it’s more likely your ISP is cheaping out on their backhauls and last mile gear so that at “peak” and throttling you somehow). This shouldn’t happen on a per-account basis, or on a per-logged-in-status basis, or on a per adblock installed basis… although your ISP can probably easily tell if you have adblock, I doubt they’re technically advanced enough to figure out a way to exploit that in a meaningful way.
Same things apply to packets from you towards Google, Google’s position is generally along the lines of “keep it up, send more”, but sometimes the ISPs cry foul either legally, or technically by throttling individual tcp/udp flows… That shouldn’t apply to browser/account. Google might be throttling YT bandwidth to not DoS the ISP (… or the carrier ISP is using on some places, although most ISPs just peer directly with Google and don’t pay a carrier for transit).
I’ll try file a bug internally pointing at the issue, but I won’t be able to followup on specifics here (it’s just not my place to do so). You can ask me other, technical, non specific stuff if you’re curious.
Throttling bandwidth just because of adblock and throttling video just because firefox != chrome is against some of the non widely externally publicized internal core product principles. (it’s just not good for Google in the long run and doesn’t really save Google anything in the short run either, I’m doubtful it’s what’s going on… it’s actually actively bad for both advertisers and consumers in the short term, and bad for publishers long-term… and short-term cash would flow from Google to publishers on these cases… highly doubtful it’s intentionally done).
ISP requesting throttling during peak hours… makes more sense, but browser/logged in shouldn’t matter… unless this is a misconfigured experiment.