Not being an engineer, or a mechanic, but being on STW, I’m perfectly qualified to comment.
I would not be surprised, if it WAS less economical and rather a product that has been created to generate a perceived need, rather than meet a demand.
Mine counts how many seconds it’s been ‘off’ for. There has to be a point at which the engine being off becomes an economical saving, but funnily enough there is no mention of what that is anywhere in the literature (yes, I did look!).
Plus, I manage to unintentionally trick mine a few times a week where the engine shouldn’t be off and I find myself pumping the damned clutch to get it to start again.
I’m more impressed that all the other functions (power steering etc) continue to work. How much power does that take?!