Your sources are all (I think?) about the fact that the way they deal with air is good, and you may well be right that it's cleaner than in your office. That doesn't mean that it's not less clean than when smoking was allowed - it may well be that in order to get rid of the smell of smoke they needed to clean the air way more than technically necessary, and that therefore after the smoking ban it could be lowered without being "some nefarious intent".