ProgressBarAttributeDrawer, "CustomValueStringMember" attribute, does not pass current value

It would be great if "CustomValueStringMember" worked the same way as "ColorMember".

Please see comments in code:

[ProgressBar(0, 100, ColorMember = "GetHealthBarColor", CustomValueStringMember="GetHealthBarValueString")]
public float HealthBar = 50;

private Color GetHealthBarColor(float value) //passes in current value
{
}

private Color GetHealthBarValueString(float value) //error, expects parameterless method 
{
}

1. Latest
2. Beta
3. No
4. Win 10