You are right and wrong.
You definatly have an argument about it beeing immersive. But there are three things:
1. I could say "why have I lost the ability to craft 'x' after i died that makes no sense" but I could also say: "after this near death experience i still have a concussion which means I learn slower"
It is all a matter of how far your suspension of disbelieve is willing to stretch.
but more importantly
2. while it was "more immersive" it was still not immersive, I just saw myself get eaten by zombies. No way in hell did I survive that.
but what is most important:
3. fun trumps realism
in this case.
The realism/immersiveness gain of this penalty was incredibly small. I never actually thought of your explanation before and I think most people haven't. Because it does not logicially lead you to that conclusion, even if it could be a valid explanation.
But this system did decrease the fun a players has DRASTICIALLY. For 15 minutes, you forgot recipes (needed to wait until beeing able to craft certain stuff and the right quality again), you were slower because oyu didnt have as much stamina, less inventory so even if you got back to your backpack, you were most likely overloaded, dealt less damage farmed less...
basicially it felt as if you were wasting time. Do you want to know what I did when I had that penalty? I tabbed out, waited until I was able to craft and run and farm again and continued afterwards.
It was basicially the definition of anti fun.
And that is why an unimmersive solution is better than a barely immersive anti fun one.
Yes it is kinda arbitrary... but you can just see it as a "blunt head trauma caused me to lose some memories of the last hour" or something.