Age and petiteness. Find an 18 year old with a size 6-8 figure and they are usually tight as fuck.
Dress size got nothing to do with it
Age is definitely a factor its all down to pelvic floor muscle
Tightest cunt I ever had was a size 16 hooker called Emma from Oldbury she was 32 never felt anything like it
I've fucked teen/early 20s & many have had wizard sleeves