Yes, for the purpose of talks round here, feeding explicitly refers only to using units for levelling, cost reduction and skill upgrades.

Also, you might want to try your hand at current event a bit. Even grinding the first map, 25 fangs required to just get the princess of the event to join you is pretty easy to get. And while minimum-reward version of her might be bloody expensive to field, she most likely than not will be your best (and only) princess, and they make dam' nice duelists. Still not necessary, of course, but nice to have nonetheless