What people want identified is the content, not the time slot. We are used to thinking about the time slot being synonymous with the material, but with EPGs, the box can handle the mapping. This indirection also allows the box to adjust to changes in the schedule. In the few cases where one needs to identify a particular showing, the proposed scheme can deal with it in the obvious fashion. No, it relies on mapping tables.
All resolution is handled in the receiver.
Perhaps what's really being stated here are requirements for software environments that use TV URI's. You are correct in pointing out that there is some mixing here, but the requirements do affect the solution space. This question can only be answered by the content creator. You then query each resource to determine its characteristics. Seems that if the protocol is going to require this, the protocol should define it as part of the resource identifier.