Which I have already done whilst trying to find a solution!! Thanks for the reply. it's great to know that this has been replicated elsewhere. I suppose the issue here is where does the fault lie? If the profile is set to not allow Safari, yet it is being used (sort of) through another app, then you'd say that Safari hasn't been blocked. Is it the Profile or is the app that gives you access?
I believe it's the app. When Google Chrome is chosen to open links, it opens it as a new tab in Google Chrome. When opening a link with Safari, it opens a Gmail specific browser and does not open the Safari app itself.
From what I can tell, the profile is doing exactly what it's supposed. Because of that, it would seem the fault is with Safari having it as a feature. I'm sure it's working exactly as Apple intends, meaning we most likely can't do anything about it.