I've heard this theory before. However, there's a problem with it: based on what we actually saw in FC, it's doubtful that without the Starfleeters' help, Cochrane would even have made his flight at all. He's shown not only to have no real reason to do so, but that he actually hates flying. And he's inebriated almost 100% of the time. And he's a big freaking coward. The only reason why he ended up doing so, and in the specific time it happened (for the passing Vulcan ship to notice it), was because Picard's crew basically forced him to to "preserve" the timeline...the implication being that this was the "real" timeline all along. Which is why the Enterprise-E returned to its own time in the Prime universe, not some other, parallel universe based on their actions in the past, a la Marty McFly and the sports almanac disaster.
.