I've received a comment from Christopher Lawton (YouTube's communication manager) who says in no uncertain terms: "loading delays experienced by Adblock and AdBlock Plus users are not caused by our ad blocker detection efforts."

That's to be taken with whatever pinches of salt you deem fit, though there's been some compelling evidence surfacing on AdBlock's github page which suggests that YouTube is innocent in the whole debacle, past transgressions aside.

As highlighted by beepingcomputer, the issue trackers on GitHub for both AdBlock and AdBlock Plus have been reporting problems with the extension's latest updates (5.17 and 3.22 respectively). This was further highlighted by Raymond Hill of uBlock Origin on Twitter.