Why do you only sometimes get to choose channels for SP?

I haven't figured out the pattern yet..



Why can't I choose patterns for a SP in all places where I can set a SP?



I *think* that if I enter an item in the To Do list, then go to SP inside that, then I can change a SP to all channels... but if I'm simply viewing the guide data, I can try to get a SP, but it won't let me choose channels.. (But again, I'm not 100% sure of that yet.)



This is on a Roamio Plus..