Well I was wrong!!
Pycharm still requires me to use that command after rebooting a couple of times.
Pycharm seems to get confused between Python and Python3 versions which affects which interpreter is used.
I have never had this problem with some other distros that I toyed with.
Are there any Pycharm/Python3/tkinter users here?
Which Pycharm installation should be used, from the software manager or downloaded from the Pycharm webstie??