

Yes, you’re correct if we want to get technical.
However, I have a difficult time believing that most people truly think that using sentence ending punctuation is default passive aggressive. If I wanted to, I could read “great.” and “great” both as passive aggressive. The default takeaway of a response shouldn’t be negative, it’s just an answer using a rule that indicates that I’ve stopped my reply.
A good reader looks for context clues to decipher meaning. In the end, if one is unsure then just ask for clarification. Starting with a default negative view indicates to me that there is something deeper going on with that person.

Dude, you’re supposed to see a doctor after just a few hours.