With a DVR? Yes.

When ads are a distinct bit of content recognized by the client, then the casual user with the stock client/no add-ons can’t overcome the UI choice to block you from seeking unless youtube lets you. But this allows ad blockers to skip even downloading the ad, because it’s clear what is content and what is ad.

If the ad is completely “just part of the stream” with zero indication where ads begin and end, then you can at least seek back and forth, with not even the official client able to block you from seeking, because it doesn’t know where the ads are either. The client downloads the stream.

If the stream is accompanied by some metadata letting the client know when to block seeking, then ad blockers can use that to auto-seek.

I suspect the last one is going to be the case, because they both want to limit seeking during ad, and they also want to change things to an ad experience so that you ‘click through’ to what the ad is trying to get you to do.