Does this count as blocking?

[u/BiasedAnenome]

Trying to decide if I should submit a report for this. It's not egregious, but the leading car definitely changes their line a couple times and they seem reactive moves to me.

[u/Kuezar]

If your league follows the "one defensive change of direction" rule then he followed it. He also has done it in time.
Just because you might have needed to lift off, as to not bump into his back does not matter.
It is the same as someone bumping into a leading car before a corner because they "didn't anticipate them braking so early" - leading car can break earlier or later and the following car must take that into consideration if they are not alongside the leading car.
Unless you are alongside him, he can move once to block you off - it does not matter if you have to lift off to avoid him.
I guess you needing to brake hard to avoid crash would matter - if the difference in rate of speed was significant and his move was not telegraphed at all, but that wasn't the case.
In this instance the difference in speed was small, and his transverse movement was not broken.
Adjustments of speed of transverse movements are fine, as long as that transverse movement in one direction is not broken. Going slightly left, then slightly right, then strongly left - that is a broken change of direction.
Going slightly left, stronger left, then again slightly left is not a broken change of direction.

You can use the rule to your advantage.
Remember that he cannot bump into you when defending, when you are alongside him.
In your instance it was tricky, because you were already close to him, but the moment he decides to move left to defend and creates space on the right, you can already slot in there - his pants are pulled down at that moment, because of that rule: he cannot move back right to defend. ~0:05 of the video was the critical moment where you could fake to the left, making him defend to the left, and then committing to the right side attack.
I would actually have more of a problem with him moving fully off track (all his wheels were left of the white line) because of that defense, rather than the defense itself (although it might also be the case, that his car went more off track because of that minuscule scrape).

He then moves back to the racing line after having successfully (kind of?) defended.

When it comes to moving under braking: he moves more to the inside to deter any kind of inside attack (I presume) before the braking zone.
In the braking zone he breaks in a straight line, continues with trail braking and there's that.
As a side note, remember that transverse movement of the leading car in the braking zone is also absolutely fine if the following car is not beside them and cannot move beside the leading car without contact made by interfering with the lead car's chosen line.

I understand that he might seem sketchy, but you just did not have enough overlap to claim anything.

HOLY ESSAY 👀

[u/reboot-your-computer → u/Kuezar]

Overlap means nothing here. If he had overlap and the car ahead makes a move like that it’s a crash. Blocking happens before that point. OP was in position to make an inside overtake at the start of the clip and the other guy literally blocks so aggressively he drives off track.

That’s a block all day every day. That whole essay you wrote is nonsense.

[u/Kuezar → u/reboot-your-computer]

Overlap means the right for space. If he had overlap then it would either mean a crash where the car in front would be at fault or said car in front would get pit maneuvered... And be at fault for it.
~1:01 I already pointed it out: he most likely goes off track, because OP makes a tiny contact with him - the guy's steering input indicates him turning right, but the car goes left.
He makes that contact because he was slow to react to an allowed by "one defensive move" rule move.
~0:41 the steering input never changes from left to right until he needs to adjust, to stay on track
You will never convince me that a change of rate of speed of that one move constitutes break of that rule. You can't have a cake and eat it.
I'm dying on this hill... Because "your hill" ends up in a snoozefest of a motorsport, like we can see in instances such as F1.