If you knew there was a dead person next door you might be a little uncomfortable, but could go about your day. If you knew there were 50 dead people next door you would need to get out of there.
The number is relevant, not just the proximity to the closest one.
Nobody panics when things go "according to plan." Even if the plan is horrifying! If, tomorrow, I tell you that, like, you'll walk through a graveyard, or a morgue, nobody panics, because it's all "part of the plan". But when I bring ONE corpse to a job interview, well then everyone loses their minds!
People are often uncomfortable in graveyards and, for example, would not want to walk through one at night when they would be willing to walk through a field.
The dirt does provide a sort of insulation however, as people would be more willing to walk through a graveyard than through a house that had the same density of corpses in the basement. It's the theoretical accessibility to the corpse that plays a factor here.
I think it would depend more on how easy it is to open the coffin. If the lead lined coffin has well maintained hinges that allow it to open with little effort, that's less acceptable than a wooden coffin that is nailed shut.
Corpse acceptability is inversely proportional to corpse accessibility.