Basically, if crew is ejected, only the Veterancy of whatever they were crewing is considered.
If the survivor/pilot/crew is listed as VeteranInfantry for a country, survivor/pilot/crew doesn't consider that; they'll get whatever Veterancy the original unit had instead.
This is not how it works in base game; crew considers VeteranInfantry listing there.
Not sure if bug or oversight or intended.
Basically, if crew is ejected, only the Veterancy of whatever they were crewing is considered.
If the survivor/pilot/crew is listed as VeteranInfantry for a country, survivor/pilot/crew doesn't consider that; they'll get whatever Veterancy the original unit had instead.
This is not how it works in base game; crew considers VeteranInfantry listing there.