Is that true in all cases?

It seems for example for Cost-per-mille (CPM) advertising if a user has an ad-blocker, they will not see the ad, but it would still count towards the number of impressions if the ad request is made?

The ad space is dominated by a few companies and all do that as far as I know.

The other dominating ad space is spliced into videos and they certainly know you will skip around if you can on YouTube.

> If a request is made

It won't be made that's what adblockers do. Or it won't land in the case of pihole/DNS level blockers.

Otherwise it wouldn't speed up browsing and tracking would continue unhindered.

There's some adblockers focused on disrupting tracking and those will both intentionally load ads and automatically click on every one of them for you.

https://adnauseam.io/

Neat idea, I'd worry that the tracking is worse than the benefit.

That said I routinely let long YouTube ads play while I go off to do something else. Personal best was circa 1.5hour ad!

Someone told me that costs them big bucks so long as it's not skipped.