That makes no sense. They have it all backwards.
Most productions companies either film in HD or convert/edit in HD now.
When DirecTV first started adding tons of HD (2007, right?), many of the channels might have had only one or two programs on a week in HD. Some channels (Fuel, I think was one) simply didn't have ANY HD programming at the time.
By going ahead and producing this programming in HD, they can have an archive of HD programming for future reruns or syndication sales, as well as for potential overseas customers, Blu-ray customers, iTunes customers, etc., or in this case, VOD, in the present.
AMC started out by offering "Mad Men" in HD via VOD prior to launching an HD channel. They later released it to Blu-ray as well as repeated it on AMC-HD. "Stargate Atlantis" was filmed in HD from the start, and shown in HD in Canada (among possibly other countries), but it took a while before Sci-Fi (now Syfy) had an HD channel to show it here in the states. The complete series is now available on Blu-ray, and it aired in syndication on multiple channels.