In my org [1], "shift left" means developers do more work sooner.
So before we clearly clarify product requirements, we start the build early with assumptions that can change. Sometimes it works, sometimes it does not, which just means we end up net neutral.
But an executive somewhere up the management chain can claim more productivity. Lame.
[1] I work at a bank.
I think that's a myopic view. Getting something anything in the hands of your potential users that's even vaguely in the ball-park of a solution shaped thing gives you extremely valuable information both on what is actually needed and, to me more importantly, what you don't have to build at all.
I consider it a success when an entire line of work is scrapped because after initial testing the users say they wouldn't use it. Depending on the project scope that could be 6-7 figures of dev time not wasted right there.