When I saw this issue I had to try for myself. I discovered that is it true but it didn't required the zone window to be open, just the turf application running in the foreground was enough. I opened the settings for the clock, put the time 1 hour forward and all the block zones disappeared. For the sake of science (of course) I also try to take the zone but was unable to do so. The "Taking zone" window popped up but no "Zone taken" window appears. It was just the "Taking zone" window that was flashing in the same way as it was doing during the period of troubles with the round start, when the block wasn't showing because the server couldn't keep up.
Flashing sign.png 1.3 MB