The only MP of mine that's double-taped (double-taped on both sides) is MP-24 Star Saber, which I got from Amiami. As far as I can tell, none of the sticky tapes on that box were cut, so i can only guess that it was double-taped in the factory just to make sure both ends are secure.

I bought my MP-28 from TLTC, and it was single-taped on both sides.