[Orry Verducci]

The difference here is that 101-105 have to be listed on the EPG, as required by Ofcom:

EPG providers must ensure that the five national general entertainment PSB channels (BBC1, BBC2, Channel 3 services, Channel 4 and Channel 5) are listed in the first 5 slots of the EPG.

Source: Source: www.ofcom.org.uk 

Sky and Freesat could argue that they have met this obligation by assigning 101 to BBC One, and blame the non appearance on the EPG on SD boxes on the users equipment being unable to receive the service rather than the platform not meeting its obligations. Much in the same way Freeview TV's don't show channels 1 and 2 if the viewer can't receive the PSB1 mux.

It's open to interpretation though so it'll be interesting to see what they actually do.