Sometimes things behave a little differently in teach mode. I've never seen anyone use a time based motion command like that. I'm not sure there are any real world use cases for that.
I found only one use of time based motion years ago in a press tending application. The robot moved into place under the press and waited for the press to finish its cycle and open. The press opening motion was time based and the robot start and end points were taught with a time based move to the end point that matched the press move time. It worked really well.
Other than that, I haven't had any other instances where I used that instruction.