Some people even created a thread for posting opinions about it. It was right in front of you:
At any rate, Destiny may be correct: sometimes a sale is just a sale.
The deep discount (double the normal) and very short term, as well as not listing it on launcher or in emails makes it look like an experiment to me. They even emailed me yesterday about the 50% Omega/MCT deal without mentioning the Omega/Plex deal.
So guessing they either want to see how much Plex a sale like that sucks out of the system, or they’re planning on a Plex sale coming up and want people to burn some now, or they’re feeling antsy about the “Players leaving? It’s summer - they’ll be back” dismissal and are trying to jump-start the “they’ll be back” process.
Or because they’re CCP and they have strange ideas and enact them on a whim.
Still boils down to “buy Omega now if you’re using Plex for it”. You’re unlikely to see a better deal for some time.