Should custom month and year picker be inside a dialog box?

I'm working on an application that allows users to sort their photos.

Please note that in the mean time, we hit a technical hurdle where an actual calendar is not possible to implement for an MVP. But for now, we'd still at least like the user to be able to input custom time periods, but limited to month and year only.

In addition, we offer other preset date ranges like - Any time, Last 7 days, Last 30 days, etc. When one is selected, it applies the filter immediately. There is no confirmation button.

How should the "Custom" option behave?

(A) When "Custom" is selected, a dialog box appears right below it that allows the user to input custom month and year. When they click "Apply", the dropdown value changes to their custom selection, and the filter is applied.

This works very similarly to Gmail filtering, just that Gmail has a full calendar date range instead of just month/year filters.

B. When "Custom" is selected, the month/year fields show up right next to it. User selects a month/year, clicks "Apply", then the filter get applied.

Both are pretty much functionally the same except for the presence of the dialog box in (A).

My concern about (B) is that since the rest of the filters get applied immediately, "Custom" will be the only one that has a button that's within the same hierarchy. So while it's functionally the same as (A), the hierarchy of it all feels incorrect.