Fun Fact: before TSMM officially opened, I happened to be in town. While at DHS, I counted about 12 CMs in Pixar Place in TSMM costumes. Each one said no soft openings that day. There were soft openings within the hour.
TMs and CMs can tell you "no soft openings" all they want. They do it so you don't have an unreasonable expectation of riding when, as HTF has repeatedly pointed out, these things are constantly in flux. Basically, while the attraction staff is there and there are no issues with the ride, softs can happen at any time.
The day will come when they do, in fact, have soft openings and at some point that day, a TM will have told a guest that there wouldn't be any.