I’m not Boston, British, or Bernie
Bernie adds "r's" actually. Take how he pronounces "Nevada" as an example: "Nevader."
Actually my aunt, grandma, and mom do the same thing. That's being raised in Brooklyn for you.
My parents do this constantly and it makes us cringe. We'll tell my mom the correct way in public, and it's all "What do you mean? It's..." and back and forth and continue to be incapable of saying words right. This is going to be so much worse in 25-35 years.... Weirdly, it doesn't bother me as much when my grandmother so done voices may pull it off.
(Not really a speaking thing, but the much cringier and painful thing is when an "-ed" is added to an irregular verb. This will send me into a fury.)