None of that has anything to do with shooting in HD. In fact, many of
the newest HD cameras in use are smaller, lighter, and less expensive
than the SD cameras bought a few years ago.

There are also cost savings that come from using cameras which record
onto solid state media or HD discs (bluray). These are not subject to
the same environmental issues of tape recording, and they save massive
amounts of time at the beginning of the editing process as they upload
into the editing servers as data streams. Video tape recordings have to
be digitized in real-time.

Considering the amount of footage shot, that is a huge number of hours.
Probably easily in the upper hundreds of hours (likely in thousands over
the whole season), that can be avoided by not using tape. Even in
smaller productions such as one hour cable shows shot in simple
environments at primarily one location (think home improvement) the
time/money savings from not having to digitize from tape in real-time
are considerable. That is just the beginning of the value for there are
many more issues of streamlining post production using tapeless cameras.

This is a case where a major network's show is a dinosaur being
eclispesd in - at least - post production cost savings and efficiency,
as well as future-proofing, buy smaller network and cable channel shows.