The display does not switch off immediately when the button is pressed, but goes out unnaturally slowly. After the set timeout, it will personally turn me off normally. However, I have 30 seconds set and I usually use the button.
Note: There are 2 variants of S3 Neo, GT-I9300I and GT-I9301I, called also S3 Neo+. Obviously only the latter one is compatible with this port. We are working on determining if we can support Gt-I9300I as well.
But you can try and contact the porter and work with them to try and support your device as well.