Hmm seem to found some info, although not what I wanted....
6.3 Analog Program Copy Protection
REQ9 The OCUR SHALL reset all analog copy protection status after a channel change.
REQ10 The OCUR SHALL detect the analog copy protection status of the selected NTSC channel
and protect it according to Annex A.
Essentially, The OCUR spec requires that the OCUR honor things like the CGMS signal on an analog channel (which will likely result in an encrypted recording), even though a non-OCUR analog tuner would record it just fine.
So its seems there can be copy protection sent over analog and the newer 2250 card is reading it where the older 1250's are not.