As
@GreyGhost suggested, it's likely just part of the bigger bucket. When you're trading in a car and buying another there's lots of numbers that can be tweaked to make other numbers more appealing, or simply changing them outright. If the dealer stands to make $10K on a new vehicle sale, yeah, I'd say a salesperson might decide to flat rate the "required" certification on the old car for fear of that customer being ****** at a $250 cost and deciding to go elsewhere.
I see the dealers issue when taking a trade in - Shop B doing a dodgy inspection or just being sloppy might end up certifying a vehicle that actually wasn't certifiable for some reason, leaving Dealership A holding the bag after the customer has already signed the deal on their new car and is history. Now they need to certify that car when they sell it to someone else and discover that (for example), the rocker panels are actually not structually sound and now the car needs $10K of body work to be
actually safe.
There's also the issue of the new safety being all digital now - you no longer get a piece of paper, it's just entered into the ministry's computer system now and it comes up when you go to register the car - I just went through that part, and I watched the lady at the Service Ontario lookup and confirm the safety in their computer. Aside from the receipt from the dealership stating "safety passed", I had nothing paperwork wise.
All that said, when this is all said and done,
no shop is actually certifying a vehicle at trade in as those safeties are only good for 30 days, so if that car sits longer than that, they need to go through it all over again, and with this new system they can't just say "we did it 8 weeks ago, it was fine, just write the paper now", either - they actually need to
DO it again. So the "safety inspection" they're doing at trade in is probably little more than a 20-30 minute lookover to make sure there's nothing major wrong,
and then they do the actual safety when the car sells. This is also very likely a contributing reason to the cost of the "required safety inspection" being negotiable, as it's doubtfull it's the actual real inspection at all.