Should the default Field initialization value be a FillValue?

The question is in regards to when a field has been declared and the memory is allocated, but before any values have been assigned to it. I think that the default is to assign 0.0 as a placeholder. Should this instead be the FillValue?

If the default is zero this can give the false impression that some fields are in fact zero when they may have just not been touched yet. Which would be a difficult bug to catch. But if they are masked values they will pop up in output as something worth investigating.