Right now double turns are blocked in Freestyle and double turns are only considered double turns when the round ends prematurely:
the instructions wrote:The player who triggers a new round is not allowed to take a second back-to-back turn and must wait for someone else to play.
Anything else is considered a "fake double turn" because the round ended naturally and all players were aware of the exact time when the new round begins. So theoretically they could go online at that moment and prevent the double play.
Having said that, fake double turns are considereed by many to be unfair and is something I've been meaning to re-visit for a long time now. Hopefully I'll find time to do something about it in the upcoming update.