Not all Honda engines, just these HRX machines with the BBC. Every one I've seen new out of the box surges at idle from its first tank of gas. No way it is a carb issue shipped like that.
I do agree that the surging in the video was pretty extreme, and it would get a bit better with new carb.
I don't think it is strictly related to the low RPM, just that there is almost no flywheel weight on these setups with the clutch disengaged.
If there were a real lean condition, it would surge with the blade engaged too.
And you're right. Cleaning these carbs really isn't worth the effort at the replacement cost.