Thats where your wrong bud. The FAQ specifically is talking of wounds
Q: When making a Shooting attack against a unit, can Wounds
from the Wound Pool be allocated to models that were not within
range any of the shooting models when To Hit rolls were made (i.e.
half the targeted model are in the shooting models’ range, and half
are not)? (p15)
The bold parts explain how the answer isbeing derived. So for initial shooting purposes for a model to SHOOT yes they have to be in range. HOWEVER wounds can be allocated to models as long as the model is in range for the WOUND POOL. So if the half of the unit is out of range of the bolters in normal cases they couldnt die per the FAQ. BUT if you add in a long range weapon that other half of the unit is then added to the WOUND POOL and henceforth overkill wounds from the bolters can indeed kill lobger range targets.
Yes, I understand we're talking about allocated wounds. Yes, I understand what you are saying. No, that doesn't change any of my answers (which mostly, I think has us in the same place, but through a complicated set of steps, and I don't think it's clear)
If you want to be super, SUPER technical about it, I think a heavy bolter would be a different Wound Pool than a bolter, because it's AP 4. Or maybe that's only true if some of the targets have 4+ save. So do we have to break down each wound pool by the weapon range to?
Anyway, see what I mean? Maybe you don't. But yes, I see what you're saying and not i don't think it's clear, even though in the end i come to the same conclusion (sorta).