I believe this should be the standard for any CEO who wants to say they take accountability.
Just because someone is responsible for something doesn't mean they need to be punished.
E.g. if somebody is committed of a crime and says “I take full responsibility for my actions” to the judge just before being sentenced, then that is a very strong signal of character for me.
But if somebody says “I take full responsibility for my actions” just before jumping in an Uber to go to a luxury dinner with the board of directors, then that does not impress me and I perceive it as a cheap attempt to reap the social benefits of saying that phrase with none of the potential costs.
My initial instinct is that this line of argument is more like venting than it is any kind of real suggestion for behavior change.
It's basically making the layoff about themselves, rather than the poor sods who just lost their jobs. (There's some other common patterns in that vein too, e.g. "this is the hardest decision I've ever had to do".)
If you want to acknowledge being at fault, that's totally fine. Just write the facts. The over-hiring was a mistake, and you're the one who made that decision. Don't dress it up into a personal journey of failure and redemption.
This message did not make such obviously false claims of accountability. Is that enough of a difference to make up the entire difference in the entire tenor of the conversation? I don't know. But it is at least the reason for your specific example.