We have some mandatory fields in the application form but they are empty, how come? → Data Validation is on and records are not verified

CRM Data Validation is based on CRM Contact / Company Form. It is not based on Individual / Company Member Form.
A field is validated only if it is part of CRM Contact / Company Form. So if a field is only in Individual / Company Member Form
but not in CRM Contact / Company Form, that field will not be validated.

In other words, Member only fields are applied
immediately, whereas common fields for Member and CRM are validated.