Even then, I'd argue every alien we've seen so far is entirely unconnected to this hypothetical staged meteor.
I keep coming back to the 'Golgafrincham 'B' Ark' scenario from The Hitchhiker's Guide to the Galaxy.
All of the aliens we've seen are kind of...
dumb. Or officious, or lazy, or otherwise jerks and largely useless. Suppose their culture decided to 'purge' their home planet of some or all of this group of people, and set up (or took advantage of) a meteorite headed toward Earth to engender goodwill in humanity. Then they said to this group, "we've just saved a planet, all the locals will treat you like kings, why don't you relocate there and have an easy life?"
It would explain why we're not seeing any particularly shining examples of alien-kind. It would also explain why the technology gap exists, since (presumably) few or none of the transplants would be technically inclined and capable of sharing much that really advances humanity's technological level. And it serves as a safeguard against discovering a supposed plot to stage the meteor strike, since the transplants are as much in the dark about that as the humans.
[Note that in HHGG, this ends badly for Golgafrincham, as everyone remaining on the planet dies of a virulent disease contracted from a dirty telephone (since the telephone cleaners were among the group sent on the 'B' Ark for resettlement elsewhere).]