Custom data Booleans do not honor default No

Create a Yes/No field in a custom field set. Put zero for the default value (i.e. No).

Check existing record, or create new record: the default is NULL not 0.

The NULL is not always relevant (e.g. my current application of this is "Is child deceased?") - it would be better if the default was honoured as otherwise it's opening up to significant data entry errors (oops I clicked Yes).

This behaviour is shown in 3.2.3 (my install) and v29810 on the demo site.

Also, any reason why such booleans are implemented as a 4-byte signed integer? Surely BOOLEAN? or unsigned tinyint(1) or even ENUM('No','Yes')?