Don't know how many have implemented FAMily_asChild.STATus, but only one (that I know of) has the feature integrated into its export/import of a GEDCOM file.
So what I'm saying is not actually what you think I'm saying. Right now, FTM does not have a Child_Family_Status. But if you or someone asks to have this type of status implement, then be sure to say that the information needs to be implemented in the GEDCOM Import and Export correctly.
This is the same thing they refuse to implement regarding married name. I send a GEDCOM with a name.type of "married" and they drop the tag, so FTM never knows that I've given them a married name and they then generate a married name by using the spouses surname. Which in non-USA terms could be very wrong. I can go on and on about these things.