There's a check in the FargateProfile constructor which only uses the subnetSelection prop if the vpc prop is defined:

However our docs don't make this clear, which lead to customer confusion from having all of their private subnets be selected. We should clarify that the vpc prop also needs to be defined for the subnetSelection prop to work.

Additionally, we could throw an error if the subnetSelection prop is defined and the vpc isn't, but I'm not sure if that would be a breaking change.

This is a 📕 documentation issue