Sure it would have a use in this case but instead of paying 400 bucks for a light mover why not buy a light instead?
The rest you say is just wrong. A plant needs a certain amount of light every day. It doesn't matter what footprint the light has or what efficiency.
Moving the light around to compensate a bad footprint for the space results in it needing fmore output than without moving. And LEDs are up to twice as efficient as HID. If you use the same wattage you got some crispy plants.
I've got much more than the $400 back in power savings at over 30¢/kwh here and by running the light closer it more than makes up for the extra area it has to cover with the increased intensity. An LED light needs a lot of space between it and the canopy when it's not moving so it could also be much closer for the same results without coughing up a bunch of cash for another light.
I'd have to lay out a few thou to replace my HIDs then due to them running cooler have to supplement heat even when the light is on for more costs so it makes no financial sense for me to switch. As it is a 600W won't even trigger my exhaust fan to turn on so I already add CO2 via an alcohol lamp when it's like that.
I'm not growing enough any more to need new gear. With pounds of pot stashed in the freezer waiting to be made into oil there's no need except for some CBD seeds I'd like to get going.
For people that need gear and plan to grow long term I'd be saying get LEDs too but for someone starting out on a low budget a good HID light can be had for next to nothing and might be all they need to see if they can even grow decent bud at all. A while ago the market was flooded with near new gear from peeps who decided to try growing when it became legal then found out they had brown thumbs so sold it cheap.
I've got a 5 bulb COB light that pulls 200W from the wall and an 11 bulb DIY LED to cover the other half of my little 2x4 grow tent in the spare bedroom. Once I've decided on keepers they can go into 2gal pots then downstairs under a 400MH until big enough to go into 4gal pots and under a 600 or 1000 depending on how big past grows got.