The creature in The Viewing was not an alien.
It was actually the Devil himself, or some other demon. Note the appendages that are a constant aspect of its form - don't they resemble horns, instead of tentacles? There's also its bright red colouring to consider.Perhaps the entire purpose of bringing in the four "experts," who represented different aspects of human knowledge, was for them to serve as a sacrifice, either to facilitate the demon's escape or simply as a first meal after being released. Hence the reason why they were "chosen." The prolonged sequence wherein everyone drinks, smokes and snorts a line of cocaine might have been part of a ritual to prepare the sacrifices.
After two of the sacrifices fled, however, the demon consumed Lassiter and Dr. Zahra in their place.
The Graveyard Rats episode only exists to prevent copyright conflicts with Lot 36.
Whether Lot 36 was intentionally written as a modern Setting Update or just had many coincidental similarities to the original Henry Kuttner story, it could have been problematic to go ahead with it without first getting the rights to adapt Graveyard Rats. It's entirely possible they never intended to actually film it, but wound up doing so because of how the pandemic prevented other episodes from being made.