Yeah, sometimes the TV movies produced for the networks were "back door pilots." During the first discussions about a
Star Trek revival in the 1970s, I believe Roddenberry mentioned that producing a two-hour episode as a TV movie that could be aired regardless of the network's decision on a series was something that Paramount liked because a pilot for such a series would be unusally expensive.
NBC had a series called
The NBC Mystery Movie that rotated three or four separate productions, to try out various formats for series. A segment that got "promoted" might be replaced in the rotation by a new once-a-month show.
Columbo was originally one.
They were called
"wheel" series.