It’s exaggerated.
I watch a lot of Canadian Youtube, it's totally a mix.
80% of the time it's identical to US about
19% of the time it's aboawt.
1% of the time it's totally a-boot.
With a US English ear, it's jarring. (not in a bad way) but we totally notice it.
Not eveyone does it. Linus from Linus tech tips drops one every few shows, but then Electro Boom never does. Bobsdecline does it a little less often.
It's kind of like the US and Brittish people saying Idear instead of idea. it happens once in a while