Not true. It's each battle, and eventually your materia can level up to give you up to 5 summons from the same materia. Maybe their caster equipped with Ghost of Kiev died and no one has a Phoenix down, revive materia (probably equipped to that unlucky soul), and they probably didn't do Fort Condor yet. Womp womp
Probably the most likely. Probably relied on aerith/aeris for extra healing too. Or... Maybe they had her equipped with G.O.K. before y'know, the thing.
You can only use each summon once per war.
Not true. It's each battle, and eventually your materia can level up to give you up to 5 summons from the same materia. Maybe their caster equipped with Ghost of Kiev died and no one has a Phoenix down, revive materia (probably equipped to that unlucky soul), and they probably didn't do Fort Condor yet. Womp womp
Oh I've fallen into the Healer-Summon trap before! I wonder if they were doing a hard-mode run and can't use items?
Probably the most likely. Probably relied on aerith/aeris for extra healing too. Or... Maybe they had her equipped with G.O.K. before y'know, the thing.
...bringing back painful memories of my first playthrough.