Yes, you misunderstood.
The "NTOA BLOG" (slide 6 of the FBI report) reported incorrect information, as the FBI investigation revealed.
Key findings by the FBI (as presented in the last five slides of the report):
This shooting and the two versions of it have surfaced a few times in different places. I am not sure that either account is 100% accurate. The FBI report is certainly "cover your behind" report saying that we were correct from the begining and all contrary information is wrong. The first report may have also been slanted to say it was the "ammo" not the officers skill or the other factors.
The x-rays are somewhat helpful but it is not possible to get a good reading on the depth based on a one view xray. There are bullets that did expand and stay in the body, apparently not going deep enough for best effect. There are also a bullet that stayed in the body and did not expand. So, in this one case there are questions that deserve investigation.
In general, we all know that the 40S&W with HP ammo has a good record especially from full sized Glocks. But there is nothing certain in these circumstances, so call it what you like. This is one case not enough to make any general statements.
Would an FN 5.7 at 1900 fps saved the day?
Would a .45 FMJ at 900 fps saved the day?
Would a 9MM HP +P+ saved the day?
All not answerable from the information available.
This is the exact reason that we must take the information from testing in known media, field reports (usually from PD like this one), gun choice and our own skill/comfort level for the choice.
For me, FMJ is the choice only if my gun is very small ( less than .380 ACP) or has a problem with feeding HP bullets (some .45 1911). I also will opt for a medium priced HP that I can rotate in my practice. I consider broken any 9mm or .40 pistol that does not feed HP bullets every time.
(Note: I will make every attempt to not have to find out by personal experience as to if my choice worked or not. The best gun fight is one that did not happen.)