It's possible. On any difficulty above Normal the Ai is unaffected by FoW, so it could very well be "reacting" to your colonizer on the way. Or, that planet is just next on the ai's colonization list and you get there around same time by fluke. One of the things the Ai does fairly well is colonize.
In the early days of my playing this game, I used to explore for a while, then reload a save from the start so I had a little colonization heads up advantage. Ok cheat 
In any event, I found that whether it took me 30 turns to get to a planet or a I went right there, if the Ai was going to beat me to it, it would have already done so, implying the colonization behaviour is fixed - these are the x planets we will colonize in this order - kind of thing.
What changes the pattern is if something happens to their ship (pirates) on the way, or you beat them to it, then they go for the next one on the list.
Range is also a factor. They get range buffs on difficulties above normal, which may change the order in which they choose to colonize.
