I hadn’t thought of (nor heard of) this until I read your post. At first I thought; well, that’s weird… but then, with only a few more seconds of thought I realized, yes… that’s right!
The period does make friendly texts or snapchat messages seem… terse (?).
By using the period it kind of seems like you are saying “End of conversation!”
I realize that I can tell my kids responses are either agreeable, or a bit pissed off whether or not they use a period at the end, are very very short worded or they use a formal word(s) instead of an informal version.
Example: “Did you get the last message I sent you?”
“Yes. I did.”
“Yeah I did”
“Yep”
“yes i did”
“ya”
Yes I did!"
All would have different meanings! LOL.
Probably why emoji’s became so important… by putting in the smiley face, laughing crying face, etc. it helps the recipient know how you meant your reply. (And that ever popular LOL)