Understood dialabrain, thanks. For those of us commenting in this thread for months there's been an ongoing discussion of the tab closure freezes which involved zero third party software and was confirmed to exist on fresh installs for those who were experiencing the freezes. On regular occasions, somebody would come across the thread on Google and assume that their freezes that happen in Safari were the same as those being discussed. But they would ultimately relate to third party software (usually a Flash extension) or configuration issues and didn't read the part about tab closures triggering it or much else.
Inevitably somebody who'd been following the discussion for longer would wade into the conversation and try and separate what were completely unrelated symptoms being discussed as though they were the same. Yes, the title is too broad and it's understandable how this happens.
There's a little bit of deja-vu seeing commenters discussing a separate freezing issue introduced with the 10.11.4 update and seemingly unrelated to the action of closing a tab when an embedded HTML5 video is playing. I never want to offend, as it's far too easy to do, but I thought I'd clarify the distinction when it felt it was slipping away again.
In terms of hardware, the tab closure issue appears to exclusively affect some machines produced in 2013 - 2015. It's predominantly 2014 Macbooks/Pros/Airs and I haven't seen it happen to anyone from 2012 and earlier (please correct me if it happens to anyone reading this). In such cases it's usually been confirmed that the person didn't fully appreciate how literally others were describing the cause of the freeze and thought theirs still related.
