I often set maintanance periods like this:

Expectation:
This internal maintenance period will be always active so I can forget about it.

Result:
Maintenance period starts only after "first" 13:30 after its maintanance rule activates.

Maybe there is good reason why maintenance works with partial overlaps between "maintanance period" and "maintenance rule" time intervals like this but for me it is always suprising behavior where I think maintenance is ON but it is not.