So I went and tried it. As I stated above I rarely use YouTube.
I do see the problem now. It is hard to get it just right. If anything it seems u have to be a little above or below the bar to get it to work.
In portrait mode not only does that seem abnormal for use but is impossible with a small progress bar.
It is really annoying. The only reason for it to be so unresponsive would be if it were easy to accidentally hit, but YouTube is one of the least interactive apps on the phone, you hardly touch the screen at all after you press play. It isn't an iOS issue bc the ff/rewind button works fine in the music app. I wish they'd fix it, as I (try to) use that function frequently. Why do you guys call it the scrubbing bar?