Not sure if you’re still running into this but, from my own digging, it looks like changing the memory is working. There are some issues showing it in the UI. Free memory on the instance updates in the metrics and you can double check on the instance with free.
On the Web UI, when you first load the page, it seems to pick some value (maybe the default?). Selecting a different process group and switching back will show the correct value for memory.
The CLI is weird because it only has one field for the memory so it has to pick something. The CLI should show memory and cpu per process type.