To me, when you’re on the course you’ll need to feel the correct length of swing without artificial aid. There are two ways of doing this, I suppose. One is to practice making feel like a specific lengths of swing (half, 3/4, whatever), and determining how far you hit each one. It doesn’t matter how far back you’re really going, what matters is that you can consistently reproduce that half swing, or 3/4 swing, or whatever.
The other method is to use a device that measures swing length and train yourself to make a specific length swing (the machine tells me that a “half swing” feels like THIS), and determine how far that specific swing goes.
Others will know more about which method produces the most consistent results, but my opinion is that you’re better off using your natural feel and determining distances for specific partial swings. Adding the additional step to the process, using a device to train your feel for a partial swing, seems more likely to produce inconsistency. Perhaps being able to dedicate a LOT of practice time would change that, but most of us don’t have unlimited time to do this.