Even back in 1979 -- when I was just 14 -- I knew the "science fact" label was a load of shine-ola. It was just an example of the kind of lovable flim-flam/sideshow patter that marked Cubby as an old school producer/promoter. Similar pronouncements in this mode included, "Roger is closer to Fleming's conception of Bond" and the always-reliable "this Bond girl is no bimbo; she's more of an equal to Bond."
Whether NASA says something might happen in ten years or Gene Roddenberry says it might happen in 300, it's still science FICTION if it doesn't exist, yet. And in 1979, America didn't have a contingent of Space Marines armed with laser guns, or we'd have heard about it. Heck, back then in the Carter administration we couldn't even keep our helicopters in the air!
I think this hole science fact absurdity went even well beyond Bond. I remember Jesco von Puttkamer, prominent NASA scientist and technical advisor to Paramount for Star Trek: the Motion Picture, explaining in a number of publications at great length how the wormhole effect shown in that film was an actual phenomenon, as if astronauts had encountered this since the days of Yeager and Glenn.
The fascinating part of all this is trying to figure out where the audience draws the line, and how much you can get away with. Why were people okay with a secret base in a hollowed-out volcano and a supertanker that swallows submarines, but not with a privately owned, secretly built space station in Earth orbit? Why were they willing to accept a sports car crammed with machine guns, ejector seats and about a thousand gallons of water, but NOT another car that can turn invisible? There is a line there, and the trick is to go right up to it without crossing. DAD is singularly fascinating as the entry to fail at this balancing act more spectacularly, completely, and regularly, than any other.
Indeed, where do we draw that line? For obviously we do draw it, automatically and without giving it much thought. I've been thinking about his for some time now, always coming up clueless. In terms of the fantastical both YOLT and MR range on roughly the level of a Thunderbirds episode. The same could be said of DAD, only by that time Thunderbirds wasn't hot any more and perhaps the attempt to marry the more 'serious', action oriented tone of the first part simply didn't gel well with the latter.
The only theory I have about it is that it wasn't particularly well written, directed and timed, therefore the spectacle did not ensnare as planned.