I think Hopstaken's timeline is a little off. Babylon 5 was already in its first season when the Chris-Craft stations decided to pull out of PTEN and form the core of UPN.
Also I dont recall DS9 being affiliated with PTEN, it was a syndicated show that was shown on independent stations ( some of whom did join WB and UPN) I don't see a mention of Paramount in Wiki
about PTEN just Warner Bros and Chris-Craft. Paramount and Warner did join forces to form the CW, but that was a few years later. And Star Trek Voyager was the show that launched UPN. Maybe the post's author is conflating several events?