It was more common for budget releases at least (maybe not on the back of the poster, but as a big folded piece of paper instead of a booklet).
Is Blastar this release: http://hol.abime.net/141/boxscan
? And the Overkill manual was on the back of this poster : http://hol.abime.net/2337/miscshot
I'd like to add a note to both entries about that
Thanks for sharing the info