Default tracking


I’ve started a new thread on an ongoing subject as the questions raised may have got ‘lost’ in the original message but have not yet been fully answered.

See also:features+requests, XB registered a/c
and RobK’s response in that thread.

Guys, help me get my head around this tracking by default for foreign registered a/c.
Saw N9M-ABC G4 a day or so ago and understand the given reasons for the prefix. G-HRDS is fairly frequent across the pond, noted ZK-KFB another G4 into Luton out of Van Nuys and a quick check on Toluca reveals XA-RET and XA-KIM. Just some examples.
So, to quote DBaker:
“Foreign aircraft flying in the US, by default, aren’t covered in our data feed. If there is one particular you need, we can request it but it’s not an instantaneous process. I think this is just to keep from upsetting foreign aviation organizations”

So what is default? I wouldnt have thought those few examples have been requested and they are obviously not blocked. It seems random (even taking into account Robs explaination of XA type matches with companies) although the odds favour not showing up on tracking.
As I have said before I understood that any plan filed into the ATC system would generate data unless specifically blocked (i.e Nbarred)

Or have I missed something fundamental here??

Thx IN (UK)