Sorry - I phrased my question poorly - I was talking in general rather than about this match. In other words, why did they build a roof that is designed to halt play for 30 minutes. Wasn't there a better type of roof available that closes quicker?
(that said, I've just been told it's not the speed that the roof closes its the time it takes for the air inside the arena to adjust to the new conditions.)
All seems like a big faff to me. And, given there was a good chance that rhe game was going to run into dusk, wouldn't it have made more sense to close the roof before the match started...?