Pins for "DS3231 RTC Mini"

Dunno why you’d say no pullup needed - not needed if you don’t use that signal but TBC

Active-Low Interrupt or Square-Wave Output. This open-drain pin requires an external pullup resistor connected to a supply at 5.5V or less.

Agree tots it should have been brought out, who doesn’t need it and needs an NC there can do the modification…
a7