Which is why I said provision not legal requirement, which is different. Think of it this way: –

“Smoking is now banned in all enclosed workplaces and public places”
“But all my punters won’t go to my pub any more!”
“Thats ok, we thought about this (i.e. we made a provision), we’ve carefully worded it so it only applies to substantially enclosed public spaces (for example)”
“So … and it obviously doesn’t say specifically, I can build a gazebo type shelter in the beer garden for smokers?”
“Yes! (certain conditions / planning regs aside)”

In essence yes, if a building meets X, Y and Z criteria then you can’t smoke in it, but provisions that are present in every law (not that I’m an expert on the Health Act) effectively say “although you specifically cant do X, Y or Z, you’re covering yourself if you do A, B and C”

[edit]

I wont get into more ‘no smoking’ discussions, I’d like to keep on topic. Ta