the Evoke F4 works just like the One Flow using the app, or you can stream using Bluetooth.
Maybe the older flow has hardware limitations preventing an upgrade.
I have noticed that the F4 is faster at doing things than the original model.
A problem I did have was with the iPhone app not finding the radio. (sometimes it would work!)
After some head scratching it was found that when the radio and iPhone 5 were not on the same Wifi band, 2.4Ghz or 5Ghz, they would not see each other!
I was using a new dual band BT Home Hub 4, by switching off the 5Ghz Wifi on the hub it works well!
This problem could be a hub issue as it was on early firmware, using an apple airport express as the wireless link gave no problems on either band.