I just tested it and everything works as expected. I created a docker instance of MySQL on port 3308.
When I tried to connect via 3306 port, I received:

and when updated the port to 3308, the wizard correctly detect the instance and import is made from this 3308 port:

and import process:

So I believe there is no issue with port selection in the wizard import dialog. Can you please try it on your side and let me know? If the issue still remains, please provide me with more information on how to simulate it.