different behaviour and UI between simulator and real watch?

Unfortunately the simulator is not always faithful to the real devices. Also, real devices have different UI between models, and in some cases, between firmware. If I'm not mistaken, 945 and 945 LTE originally came out with an older UI which looks like this:

https://developer.garmin.com/connect-iq/user-experience-guidelines/forerunner-2018/

But since then, at least 945 LTE has been updated to the newer UI which looks like this:

[https://developer.garmin.com/connect-iq/user-experience-guidelines/fenix-2022/]

Of course, neither of those confirmation dialogs looks (or behaves) like what you see in the simulator.

I don't have time to test it right now, but this old thread seems relevant:

[https://forums.garmin.com/developer/connect-iq/f/discussion/1386/handling-back-button-press-with-confirmation-view---vivoactive]

TL;DR, a confirmation view has 3 possible responses: Yes, No, and Cancel (triggered by the back button). (TBH I disagree with this design, but oh well. It may have made sense to cancel a confirmation prompt when it was in the form of a menu, but I don't think it makes sense when it's in the form of a two-button prompt)

onResponse() is called for Yes and No, but not for Cancel.

This (8-year old!) comment from a Garmin employee is interesting:

"I discussed the issue with the team, and because all the devices have adopted the yes/no/cancel paradigm, we are going to adjust the simulator to match that behavior"

But based on the ConfirmationDialog sample, this is absolutely not the case. When I press BACK in the simulator, that's treated as No.

Haven't had a chance to to test on a real device, but I assume that if you press BACK, onReponse() won't be called but the confirmation view will be popped.

However, I'm not sure why, in your case, this also seems to pop the parent ScoreView as well. Maybe the solution is to add an onBack() handler to ScoreDelegate which returns true.