The only reason why I have an issue with why the "executed" Warriors are alive isn't really because I wanted moral redemption or just to seem them dead, but it's because there's something that's missing. Either there's some document or nuance to the story I missed, but what they went through after getting defeated by Komaru just doesn't make sense.
Why did they get taken by the other kids just to get beaten up when they lose? Why is Monaca so weird about them being dead when they're not? Monaca's the one in control, so why did she just want to beat up the losers when she's really someone who seems like she'd rather kill them?
The first thing that comes to mind is that picture was a complete afterthought, which is why it was just inserted into the credits without any context. Maybe as a means to calm people who would have gone crazy for some reason or another if the game ended and they turned out to actually have been killed, or because some last minute idea for the Warriors of Hope in the future of the series came to Kodaka, and what could have been a surprise twist in a future game ("they actually survived!") was actually inserted into the same game as a tease.
On the other hand, if it was planned all along, the only thing I can think of is the fact that Monaca's intentions are not as she makes it seem. When she claims they're dead in such a vague way—throwing tantrums to anyone who would suggest otherwise—one is either lead to believe that they might not actually be dead and that something special happened to them, or that it doesn't matter to her whether they're alive or dead because, since they fulfilled their purpose in Monaca's plan, they're no longer of any use to her.
But, again, she was presumably the ones who made the kids assault the defeated Warriors so, if it's the latter, either she tried to kill them and they fought back, or Monaca didn't want to kill them at all. Was there any genuine indication that Monaca might actually care for her companions? The possibility that she didn't want them to die and something about how she referred to the time when they were all going to commit suicide (but she was actually going to sit back and watch) makes me think of this.
...Way longer than I thought thinking about this, but I don't know if it's a mistake or not that that picture exists, and I wish there was an explanation for why it does.