Haven't people extracted keys from TPM chips with electron microscopes? I don't know if the T2 is fundamentally different in some way which would render it immune to such analysis.

>Haven't people extracted keys from TPM chips with electron microscopes?

Once, with one brand, in 2010. And it took 9 months.

That sounds like much to me, with a 2018 mindset. Is it not pretty easy to read out a chip nowadays, even at low double digit nanometer levels?

Something "worth many millions of dollars" will most certainly be kept very quiet by the repair industry, since it can provide recurring revenue (until someone else discovers and reports it to Apple) to an otherwise extremely repair-hostile ecosystem. Bug bounties are a one-time deal that otherwise gives no advantage to the reporter, but unlocking services are not. These people are certainly not looking for a pat on the back from Apple or wanting to make its devices more difficult to repair.

Forget the repair industry, this would be NSA level interest. No one is going to repair your computer using the zero day of all zero days.

You really think the repair industry is the one sitting on that vuln?