Custom Field Select or Select Advance Required still submit on empty selection

I think I am facing a bug on custom field both select and select advance

I have a selection of

single
married
divorce

and put it as required, however both select and select advance field can still be submitted without the user selecting the choice and the field will return empty.

I tried putting select in the place holder and leaving it empty still giving me the same result, I tried to use validation required. it is still not working.

Please let me know if this is a bug or if there is a way to solve this issue.