I agree that it is unusual. The report users have asked for this ability.
I would love to have some other options available such as standard slicer with date value that allows for showing only month and year but not day, or allows for showing only 1 day per month. Even if you have a date table with 1 day per month, the slicer shows every day in the month.
Another option might be timeline visual, but there are not a lot of customization options for that either and it requires a lot of vertical space on the page.