A #12 plate is usually stainless, so hot water alone won't warp it unless you're talking really hot, like above 180F, or tossing it in a dishwasher cycle. What actually happens is the fat and meat bits cool down and harden in the burr gaps, and sanitizer can't get through that layer to kill anything. Cold rinse right after breakdown makes sense because it keeps the fat from setting up in there. The new plate and brush routine working is probably more about the scrubbing and timing than the heat thing he told you. Still, if your swabs are clean, the guy got you to a good place either way.

Did you check if the tape has the original Nickelodeon bumpers before each episode? That's usually the tell. The real banned copies floating around came from promo tapes sent to TV stations, so they'd have that weird orange splat logo and the announcer saying "coming up next on Nick." Most of the flea market ones are just taped off the air later when they did show it edited, which is why you get commercials. The "Man's Best Friend" episode got pulled before it ever aired regular, so any copy would have to be from a leak or a review screener, and those are crazy rare. You might have better luck hunting old Usenet posts from the 90s than digging through Tulsa flea markets.