I can never recall any box being wrapped in the 90's...even the early 90's...
Yes in the 70's and 80's the two parts of the box, back being the afrolex, and note that i am talking only about big sets like the framework houses, the were held together by wrapping.
I really do not know when this wrapping stopped...I guess when the boxes were all made of charton....I can also recall a set 3436 stable produced in 1985 being wrapped but it was all charton....
So maybe yes, the wrapping stoped in the late 80's....i guess...