[regularfry]

The reverse - tow plane lands separately - has some interesting challenges. If the tow plane lands first and messes up the landing, blocking the runway, the lead plane now can't land. Fine if you've planned the fuel for a round trip, and fine if there's a currently-usable second runway, but I can see a huge draw for this in being able to get interesting cargo loads into and out of smaller airfields where that won't be available.

If the tow plane lands second then it needs to loiter, gliding autonomously, for as long as it takes for the lead plane to land and get out of the way. And that sounds like a much harder problem to do safely, particularly with the lead plane's pilot having to pay attention to landing and unable to control the tow plane if it gets into a dangerous state.