QKeySequence (ie. the local action system) doesn't distinguish between them and (thus?) KKeySequenceButton and the other suspects do neither (you get "Ctrl++" whether you used the alphanum or the num block to enter it)
In a way this is a regression (because one could distinguish years before and the keys are treated different by X11 and Qt sets the Qt::KeypadModifier on the event, but status quo is that the mentioned numeric block keys are virtually dead as shortcuts.
So better take them as equivalent?
Numpad keys are now treated differently.
https://phabricator.kde.org/D6226 (for recording, and this is enough to make them work in all apps)
And for kglobalaccel, the patches are up:
See also https://bugs.kde.org/show_bug.cgi?id=183458.
*** This bug has been marked as a duplicate of bug 183458 ***