Designing silicon requires a much greater attention to detail than designing software since the penalty for bugs or a bad design is higher

3 designers per silicon org is a ludicrous underestimate

Yes, one of the ludicrous statements. I would invite him to take a look at OpenTitan for example and see how many designers work there on that thing.

Japan is not a western nation

It is impossible to immigrate to the US unless your employer is willing to go through the time-consuming and expensive process of sponsoring a visa + green card, which they have little reason to do since they can pay you less over here. I've been designing chips for years in the UK at ARM and elsewhere, haven't encountered anyone moving to the States

Oof. That is rough. I assumed Arm would give the L1/2 option to high caliber employees - it's the norm in India.