You can literally buy a rack count tray for Mac Minis on Amazon, so I’d assume AWS mounts them in racks. It’s not the cleanest model, but Mac mini’s are smaller than 1U (1.4” vs 1.75”). They are also much cleaner to rack than the old trash can Mac Pros.

(Non affiliate link to a randomly chosen example)

Mac Mini Rack Mount, UCTRONICS 19" 1U Rackmount Supports 2 Units of All Mac Mini M1 and The Previous Models

https://www.amazon.com/dp/B093GQ8TJC