I don't think this is true at all. My 1.x/2.x format keys at the same, and they activate/validate on v3 just fine. I replaced my Laptop & Desktop, transferring the key over and installing v3 fresh. I didn't have to install 1.x or 2.x first, then upgrade.
I strongly believe the generated keys aren't keys from out of the blue, they're from active 1.x/1.2 keys that users like myself still have active. And of course the current system wouldn't allow for it. It'd have to be re-developed or upgraded in a way that would accomplish this. Thus I'm making this suggestion. I feel strongly this gives License owners better control to secure their keys, rather than everyone having go through the process of getting the keys replaced when it's discovered to be compromised.
Again, just a suggestion. For all I know Malwarebytes just prefer replacing the keys one at a time as they're reported. I of course don't like it because I want to cause disruption to the piracy scene.