What is a single word for a false assumption of similarity, namely through empathy?

A very similar question was asked here, but provided phrases and was worded a bit awkwardly.

I am more inquiring as to whether there is a single world for when person A feels empathy for person B which does not align with how person B actually feels. Thus, falsely assuming similarity between their feelings.

e.g. Before speaking to Tim about the death of Tim's father, John was sad because he empathized with Tim. However, Tim was actually relieved and happy about his father's death. Tim's father was an abusive alcoholic, and constantly assaulted and emotionally tortured his entire family for 30 years. John's (word) made for an awkward conversation.

edit:
Misunderstanding is a great word for this, but is incredibly general without enough context. So, I guess I'm also looking for a word that is synonymous with misunderstanding, but in the specific context of empathy.

• Next dialogue - What is the earliest use of "You just/still don't get it do you?"
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