For collectibles locations, I think the guides are actually wrong in one specific case: Com collectibles like Lightning-Split Soarwoods don't drop in Forgotten Realms, right? Only in Eberron? So any guidance to try a dungeon in Forgotten Realms to farm those items will result in nada.
Conversely, for those tiers that include the Eberron-only items, if you are looking for a different item in the same tier, you actually WANT to farm in Forgotten Realms (everything else being equal), since the non-dropping items then don't take up a slot, which effectively increases the chances of a drop of the thing you want.
It would be good if the guide helps players in this regard.