Here is one trail that ended: https://www.foodbeverageinsider.com/formulation/mcdonalds-dr... In addition to McD's, PandExpress and TacoBell discontinued trial menu items.
> At the pilot’s onset, McDonald’s indicated the McPlant would be available as part of the pilot for a limited time while supplies last. The company confirmed to Food & Beverage Insider in August the test run concluded as planned.
In other words: they ran a trial, and it finished. That itself isn't evidence for either success or failure, any more than taking a scheduled blood test is/isn't evidence for a blood disease.
There might be some ambiguity, but the evidence needle is definitely more on the "failure" side.
This isn't like a routine blood test. They were test marketing a product. If the test succeeded, it would be foolish of them to not roll it out widely and make more money off of its now-measured success. It's very likely the product didn't meet their expectations, but it's hard to say by how much.
I don't think you can safely assume that. There are lots of reasons to not immediately turn a trial into a full run: logistical and supply chain considerations, contract negotiations for the ingredients, running surveys and tweaking the items based on customer feedback, &c.
This is true in almost every industry except software: you put space between the trial and full deployment because there are physical and logistical considerations that cost time and money.