Custom Heroes Ascended Forms
Playing an Ascended Form can indeed shorten the round. 

What that sentence means is that an Ascended Form does not immediately end the round. The round continues, but the only legal play is another Ascended Form  (which causes the following player's turn to be skipped, etc). One must match or beat the current set, and only an Ascended Form matches or beats an Ascended Form.

That said, an Ascended Form does immediately end the round in a two-player game. In a two-player game, you need to beat (not match) the current set, and nothing beats an Ascended Form.