Personally, I believe in: "There's what kills, and what kills well".
I prefer a bullet that is not more so dependent upon perfect shot placement or everything else going right. I prefer a bullet that is forgiving and still performs well when things don't go as planned.
There's always more to the death than death simply occurring, alone. If his shot placement was crap, but the animal still died relatively quick and very effectively made up for the shot placement error by creating wide wounding and a large amount of shock, that's a good bullet.
Conversely, if the shot placement was great, impact velocity was well within the limitations of the particular bullet, and every other box checked, yet the animal still ran and died much slower than desired, even with follow up shots, that leaves more to be desired. It just does. Does it mean it's a bad bullet? Not necessarily, because anomalies do still happen. It's when this sort of thing happens with frequency with this bullet or type of bullet that it becomes an issue we can tie to the bullet rather than other things.
The bottom line here is that I don't think it's right to dismiss the concerns of the OP, nor do I think it's right to flat out say it's a bad bullet based solely on this experience. Both may be true, but we should be willing to explore both possibilities, rationally and logically, rather than point fingers and jump to the wrong conclusions and getting emotional with responses.
There's even arguments going on with side tangents lol.
Certainly we can do better.