I should start off by saying that I do not play AOS, but I can appreciate some of the fluff and that the rules have improved since AOS's inception. So to the topic at hand: The Slann summon the Lizardmen (or Seraphon or angelic space lizards; Whatever floats your boat) using celestial energy. In the Thunderquake battalion they can presumably heal units with it, so why is it that we cannot do that normally with celestial conjuration points? I mean since Lizardmen is created that way, summoned that way in game, why can't the Slann just put a little more energy into a unit if some of it have "evaporated" as the unit has taken damage? It would make the army a bit more unique regarding its summoning, and give another tactical element, since you need to choose whether you heal something or make a new unit. The next logical step for a new battalion would then be one that gives an amount of summoning points for free each turn, which can then be used to either summon or heal. All this would make the Slann even more essential to the army, which is the whole idea of the faction anyway right?
Ours is not to reason why, ours it but to paint and buy. I agree with you. It makes sense. And it would be a nice rules change. Perhaps if/when we get the new codex this will be part of it.
I guess you have a point I just can't help myself Could be. It will probably be a long time till that arrives though