I'm going to speculate (Occam's razor) that the majority of their server portfolio are 32GB servers in those 400 datacenters, and so this is what they need, and

I'm going to speculate (Occam's razor) that the majority of their server portfolio are 32GB servers in those 400 datacenters, and so this is what they need, and so they documented it as a requirement. For data center migrations, this is fairly typical.