Thanks for clarifying @silta, and for the confirmation @spark. That all makes sense now.
Concerning the original bug then, I can make a fresh internal bug report to cover it. However, one thing I want to be clear on is that this isn’t just the consequence of lack of VoLTE support on your phone.
I appreciate what you say about the fact your Xperia X doesn’t suffer from the same issue, but I just need to clarify.
Currently, without VoLTE support, and without a 3G network to fall back on, your phone will drop back to 2G during a call, meaning there’s no data connection. This is all correct behaviour. After the call it should then return to 4G with a data connection.
Is the Xperia X nevertheless dropping to 2G and then returning back to 4G quickly? In the case of your Xperia 10 II, if I understand correctly you see the same behaviour except that it takes considerably longer to return to 4G (could you clarify how long in both cases please?).
I’m sure I’m repeating things that you’re well aware of, or have already covered above, but it’s just helpful for me to be certain about these points.