Photography at kpop venues

I was at Le Sserafim tonight for my first show in Korea (from EU) and thought I would take my camera (small RX100), but a friend who had been to a few said I'd be refused entry or kicked out/banned from future events. So I found somewhere to store it and went in. Cue my shock when not only was there no bag check, but 3 people in front of me had full DSLR/Mirrorless cameras, one of which appeared to have a telephoto lens (couldn't tell exactly, but like like 400mm). This was near the back of the section and next to the aisle (rather than in the middle of the block), security didn't say word.

Then spoke to a different friend who said in all the shows they've been to they've never been bag checked, even with big backpacks, nobody says a word about 'professional' cameras, and I should bring mine when we go to see Twice tomorrow.

So what's the deal? Have I just witnessed an anomaly, or is it really that unregulated? If I do find someone regulating it do they give a warning, or just drag you out?