[2020] Water flow still not implemented?

It's not being worked on currently, not sure when that was said?
It's planned to be worked on sometime in the future, but it's a low priority feature.

I can't give you an ETA, it's not currently on the medium-term roadmap. Water wheels are not affected by this feature not existing either, you are supposed to settle near rivers to use them. Updates to water have been made in Update 10 to support boats, though.