I think it's more like difference in commitment to product and sales model between Apple and every other phone manufacturers. Apple really commits deeply into making singular globally unified phones and rejecting pressures to make carrier branded bastard children of iPhone. None of Android phone manufacturers are as committed - even Google - and so unnecessary features gets removed from non-Japanese phones, even the same models were sold globally as well as in Japan(not always the case as Japanese businesspeople generally hate more to think about exports than about lost opportunities and there had historically been obscenely abundant supply of Japan-only electronics).

It's surprising that it can be added back on Pixels, I thought it would use something like factory generated certificates.