1. 60 items are too much to show in a flickable list. The user can't know how hard to flick to go directly to (or even near) the minute he wants, and one big swipe often isn't enough (you run out of screen). On the other hand you need one tap on the circle, and it's obvious where to tap unless you can't read an analog clock.

2. When you flick upwards you cover the slot with your finger so it's difficult to see what you're going to choose

3. If we had an inline slotmachine with only the selected time visible and the other values showed up only while dragging I would accept the screen space argument. In fact, I would prefer it in some circumstances (depending on the frequency of choosing times) over a pop-up circular picker but in the current situation the qml timepicker is a dialog that by definition takes up the whole screen and adds two unnecessary taps.

4. Inconsistency: There's no cancel button in other dialogs, the buttons aren't themed like the other dialog buttons, and there is no X button. That dialog is like a hastily made custom component.