What you say is so true. I think because smoking was such an obvious and total breach of school rules, it was an easy and unambiguous reason to administer something of an exemplary punishment. And awarding an automatic 6 strokes of the cane meant there was no grey area for debate! Maybe at some schools, girls got it easier than boys, but at my school they believed in female equality LOL, we got identical punishments to the boys.
I don't recall any smoking round-ups of the scale you mention - that must be a salutary experience - but definitely there were smoker groups - and when caught in a group like that, we were caned together - like in front of each other. It gives one a bit of extra courage, getting caned in front of your schoolmates, but the downside is the embarrassment.