I'm not surprised to see this and, as a current WP Engine customer, I'm happy to know it. Having the option for background updates is a good thing for Wordpress to add, in my opinion, but serious businesses want to take time to test updates versus key plugins or infrastructural elements.

A lot of what WP Engine does behind the scenes is unusual compared to the average hosting setup and it makes perfect sense that they want to apply caution. It's what I pay them for, after all.