CRM 2016 on premise, we have set use legacy form rendering to No and when we set to Yes we see a doubling in response time.

I open example Account 1 and use CTRL-SHIFT-Q view to measure performance of first opening and refresh.

Account 1 
1746 MS - 1386 MS (refresh) Legacy form rendering - YES

Account 1 
2871 MS - 3438 MS (refresh) Legacy form rendering - NO

Why is it that we get a lot worse performance with this option set to No while i understand turbo forms should increase the speed ? 
It is the same when testing other accounts, different computers, different locations etc etc.