Yes. It's an expected behaviour. In UI, property inherits the control from the Property. But here, it's explicitly changed to custom control. so, it's conflicting with the Pega's OOTB control at property level with custom control probably though not sure.
Also, you're trying to apply DateTime(Custom control) on "Date" Type property so this is getting registered in logs.
- In the "General" tab of "DateOfBirth" property, update <YourCustomDateTimeControl> in "UI Control" field of Display and Validation heading.
- You could create a new custom control of "Date" type property only to be configured on "Date" property in the UI to avoid this.
Hope it helps, kindly notify if it helps you by marking this post as answered for larger Pega audience.