Just to note:
This part of your post describing "Conventional ad hoc digital satellite delivery" actually sounds like "Frequency Division Multiple Access" (or FDMA).
Therefore shouldn't the last portion quoted above read as;
It's both. Each of the four slots can be leased out for time segments as short as 5 minutes to individual customers. That's time division multiplexing, per slot. The slots themselves share 4 narrower slices of the wider transponder, each slice dedicated to a single slot. From the point of view of the transponder, that's frequency division multiplexing.
Sorry for any confusion. The point is that since the DBS company owns or leases the entire transponder, they can remotely reconfigure it to have one wide carrier centered on a single frequency rather than 4 narrower carriers adjacent to each other, and that is received by a single wide-band tuner, whereupon the 4 separate signals are separated out (demultiplexed) at eventual playback, or separated at reception for a conventional DVR.
So wideband single carrier (containing multiple programs in a single stream) vs narrow multiple carriers (with a single program in each) is the difference between how DBS sat and conventional sat works (with DBS usually having more transmit power to illuminate the smaller reflector), but the only real difference between a "Hopper"-style IRD/DVR and a conventional IRD/DVR is that the Hopper demuxes at playback but records all of the programs at once, while the garden-variety DVR demuxes at record to minimize the amount of HDD space needed for a single program.