What you're seeing is a bit of a rare bird. DIRECTV's first move into single wire technology was the SWM-5, which as its name suggests could handle 5 tuners at once. The device was made by Zinwell, who today manufactures the SWM-8 which looks quite similar. It never reached wide distribution and was rarely seen outside of DIRECTV's own test pool.
With today's manufacturing techniques, it's not uncommon for a prototype run to get massive changes to it when it hits the mainstream. In the case of the Single Wire Multiswitch, the device was modified to provide support for 8 tuners and to put out a stronger signal. Later revisions of the SWM built all the electronics into an LNB for an even easier installation.
It seems like the SWM-5 could be a good fit for Genie, the new 5-tuner DVR from DIRECTV. Commercial installers seem a bit stymied by the new system, which requires an entire 8-channel SWM (or one quarter of a SWM-32) be assigned to each apartment that's being serviced. If DIRECTV brought back the SWM-5, there would be no waste; one could even imagine a SWM-30 where 6 apartments could share 5 tuners each.
Let's say, it's not impossible. But really, the SWM-8 probably costs the same to make as the SWM-5 did, so other than the comfort of knowing you're not "wasting" a tuner, there's no benefit. A SWM-30 could be built but it would probably be more expensive than today's SWM-32, although with the ability to service 6 apartments instead of 4 it might be worth it.
Another option would be to allow the HR34 Genie DVR to run in 4-tuner mode, allowing for 8 apartments to be serviced by one SWM-32. This might work for 1-bedroom apartments, but DIRECTV seems pretty keen on the idea that its 4-room setup is its most popular one, so 5 tuners seems like a minimum, assuming the basic notion of watching live TV in four rooms at once and recording something in the background. So, this is a non-starter.
DISH has had some success with its 3-room Hopper/Joey system which allows for only 3 recordings or 3 rooms watching live TV at one time, because for prime time it expands to allow for 6 recordings at one time. When in use as a 3-tuner system, it doesn't do a good job of working in a 4-room setup.
So, it's not likely that we'll soon see the return of the SWM-5, even though on one level it makes sense.