Interesting business as a practical matter as my understanding is that it is hard to know whether an inhibited passenger is inhibited by CBP or TSA as all inhibited passengers come back as 11 with no distinction, so did they manually clear each CBP-inhibited passenger with the TSC to get rid of the TSA no-board flag?
FRA and MUC have had CBP IAP in operation. How that played into what transpired should have been the same at FRA and MUC as at say LHR. How FBI cooperation with German intelligence/police played into what transpired for some such passengers may be rather telling, but I haven’t looked into that.
If a non-US person comes up with the TSC as to be inhibited from travel to the US, most commonly the person wouldn’t be issued a US visa or an ESTA at time of (and by way of just) initial application.