I actually have no idea if there's any truth to those IMDB stories, the '78 version of Graffiti have the Dolby system in the end credits, that's mostly why I said the end credits were slightly altered. That one is picky. ;) Btw that Dolby mix on the DVD is one of the best 2.0 surround tracks I've ever heard, I can only imagine how great it must be in lossless PCM.

At least one vintage review in The Hollywood Reporter dated the day after its wide american release in '71 mention the Buck Rogers segment: http://originaltrilogy.com/forum/topic.cfm/THX-1138-American-Graffiti-LD-preservation-request/topic/11741/page/7/