Well, he grants them power and heals them at once, it's the same action. The statement says he did so because of their potential for great magic ("
due to her potential, she was endowed with powerful magical abilities"). Please do imagine being in Hyness' shoes; 3 girls are dying around, we're told you saved them bc potential for great magic, not bc you cared for their security, or bc it was the right thing to do. We got 3 more descriptions about that backstory, they say you gave them power rather than how you healed them or took them away from harm. What does this say about your character? It says it either didn't care about them, or you mostly only cared about your own personal benefits, which technically leaves room for some care for them. But then, that care is so little, it kinda doesn't matter;
The girls are put in a dangerous military position when they grow up, which can be assumed to be the goal all along. It's not like we're shown Jambastion cult members with great magic assisting their society in a non-combative way. So Hyness can easily be said to already be thinking about putting the girls in deadly perils at that point in time. If we assume his travels had that goal in mind from the start, then this goes even earlier in time.
Bc of his worsened madness, it's hard to attribute his actions in Story Mode to a regular version of himself. But we do know he sacrificed the Mage-Sisters to Void and their devotion was so high, the Mage-Sisters didn't call him out for it. Considering Zan Partizanne's sacrifice of his army on Jambastion, and how she isn't portrayed as worsened by madness, we can assume this is at least in line with the teachings of these people. Also consider how the enemies inside the collapsing Jambastion were still fighting you as Kirby & co. were running away, disregarding their own lives. Their teachings may not tell you "Sacrifice your own people if needed to," but they're so awful, that if that ends up happening, nobody cares. That's how much "care" Hyness put into his daughters.
Also consider, when Hyness summons the sisters to use them as weapons & a shield, the Mage-Sisters already make a pose, crossing their arms as if readying themselves to be better bats and a better shield. It's like they knew this was a move Hyness could pull off. Did they communicate this with each other before? If so, was it before Hyness' madness got worse? We don't know. But even if it was after his madness got worse, Mage-Sisters were still raised to devoutly accept this treatment. That's how much "care" Hyness put into his daughters.
If Hyness cared, he would remember the name of 1 of his 3 daughters, who is also the leader of the Mage Generals, who lead the military of his whole people. Zan Partizanne should rank 1st as the most important mortal on Hyness' life. Hyness apologizing is implied to be manipulation, imagine; What happens if he doesn't apologize? He would be mistreating her and leaving it at that. He needs to create the appearance that he cares, so "because he cares," he apologizes. Not that he will learn her name in the future, he doesn't care
that much. Seems like a cartoonish display of how much he doesn't care. But even then, yes, I'm willing to accept that
maybe he apologizes bc he cares a little.