This also feels like "we're about to build a bunch of datacenters and we cannot meaningfully verify the quality of the concrete at our sites." This enables them to monitor the variables and probably not pay if it's out of spec would be my guess.

In my concrete mixer experience that's just one part of the process, lot of other crap goes wrong, forms, vibing, water, additives. I'm not pouring foundations, so my xp is only to say there's a lot going on. Guess it's a first step?