Let’s stick to what we actually know.
We could speculate all day long, but would love to see some actual evidence of this. It’s a little odd to think the same manufacturer creates 2 of the same seals to different standards in the manufacturing process.
Ok, Manufacturing 101, no this isn't speculation, this is how things Actually work.
A part is designed, machines are setup to make the individual pieces of those parts, more to assemble into the "final". Despite the best efforts of all parties, raw materials have a slight variance, machines wear and start offering up parts that have slight variance in tolerances. Toyota (and other top tier buyers) will order exacting tolerances, the best that can be produced with the best of raw materials and all manufacturing tools in perfect/new condition. Parts are tested against those exacting standards, anything that doesn't meet them is discarded (though, it's more like 1 in 1,000 are tested, that range can vary depending on how much the buyer wants to spend).
It's worth understanding that Toyota may be buying 2nd tier bearing behind the military/aerospace industry... or 3rd tier. Just as Kia may be buying/installing that same bearing that Toyota passed on (with their 10 year/100k mile warranty). A lot of the additional cost comes from the additional testing done, some from being given priority to have first (or second, or third) pick. More for having to cover the different packaging/labeling costs and yet more to cover transportation and storage on Toyota's end.
The bottom line is that all of those manufactures have reject parts that are on the bleeding edge of being rejected and opt to recoup some cost by selling them rather than scrapping them. These same companies stand to lose their big contracts if their name is sullied in the selling off of extras (and there May be a clause in the contract that states the parts must meet XYZ standards). You really have no reason to fear buying fro the OEM manufacture, and the costs are lower simply because there are fewer costs associated. Sure, you're likely getting a part that's only 99% as good as a Toyota OEM, but when those same parts have an engineering margin of ~10% you're well within the realm of safety.
I've used various ebay timing belt sellers for years, running them to 90% of their rated life (so 90k miles on 100k mile recommended intervals ~ just my own personal margin of error).
