Paradox in Ben 10 warned Gwen about 2 timelines she was about to create in episode "Time Heals" and even informed her what had happened in them + knew about a timeline he was about to create 200 years before it happened in episode "Paradox".
Paradox doesnt have cosmic awareness, he doesnt know about every timeline in Ben 10, he didnt know about No Watch Ben's timeline and he didnt know about a timeline where Hugo didnt become the trans-dimensional beast, nor does he know about Eon's timeline( he didnt know Eon was an alternative Ben).
Paradox only knows about timelines he has travelled to. Meaning he must have been to Gwen's alternative timeline before she created it, and he even took Team Ben and himself to a future possible timeline 200 years before it would even be created.
Which also fits perfectly with Maltruant describing the Timestream as infinite and Paradox saying there is an " ad infinitum" amounts of paralel universes and all of them being every bit as real as their own.