There is a clip of Things to Come in the documentary SPFX:The Empire Strikes Back, helping to show the history of visual effects before Star Wars.
This same factoid about Things to Come being used originally turns up on the IMDB, so it's may be a case of someone at TCM copying the same info of dubious origin.
Buck Rogers makes more sense, as it's set in the same century THX is set in. And we know George grew up on those serials.
And my full frame print has it too.