I had to make a new one on the spot, was no problem, but it seems that they will just approve the ESTA when applying for it, and then later refuse you if they want.
> Your travel authorization has been approved and you are authorized to travel to the United States under the Visa Waiver Program.
It then goes on to say (but this is the same for visas as well):
> This does not guarantee admission to the United States; a Customs and Border protection (CBP) officer at a port of entry will have the final determination.
Australia uses an almost-identical system (IIRC the US one is based on Australia's).
I am saying: "I agree with you that the webpage said this. The webpage should not say that, because that is not accurate or useful."
In your pursuit of antagonizing someone who agreed with you, you have now devolved into trying to nitpick details of a program you clearly don't actually understand, so I'd suggest you just accept that when I said I agreed with you that the wording was bad I did in fact mean it, and stop now.
FWIW, the last esta before the current one was not immediately approved for me. I did however get a mail after a while that it was approved and i get consistently mailed a month before it expires.
If your approval isn't immediate (mine wasn't) then you have to keep checking back to see if/when it gets approved - they don't email you.