I've done 2 systems in homes keeping both in the basement and I've had builders but the utility room on the second floor. With todays taller ceilings the ductwork can stay out of the attic.
Yes I've seen this before as an option. But with the current design, there isn't really a place to put such a utility room on the 2nd floor. The 2nd floor is huge, so it's not like room couldn't be found, but with the design as is, there's not a dedicated space. It's something I'll have to discuss with the builder.