Everything in business happens to increase sales. For retail, there’s even a name and occupation for it:

https://en.wikipedia.org/wiki/Planogram

You always want dairy and fruits/vegetables on opposite sides of the store since they’re perishable, hence they get purchased the most often, and you want people to walk past all the other aisles every time.

It seems to me that a sensible person buying a lot of groceries gets refrigerated and frozen items last so they have the least amount of melting/warming up on the way home. So the positioning of them after everything else is in the interest of the customer.

the perishables could be closer together, vs having people traipse across a store to get the basics (conveniently seeing hundreds of other opportunities to load up their cart along the way). "interest of the customer" (saving money) doesn't align with "interest of the business" (maximizing rev/profit)

Completely and obviously false (the part about everything in business is about sales). It's not as sexy, but often policies are about reducing costs. Like changing suppliers to save a few pennies per item.

If it were all about sales, then I could buy widgets for $100 a unit, sell them for $50 a unit, and call it a success.

Obviously positioning matters too (hence all the garbage food at checkout), but I wouldn't by default assume that this is the case, and especially not the only driver, behind dairy placement.