What does this have to do with maturity? The post didn't even seem like it came from insecurity, merely curiosity.
There's a linguistic shift happening where people tend to not use periods in short form communications (sms, dms, etc..). So older people who may not be as plugged in to the youth culture sill use them. So it only makes sense someone would be seen as older if they did.
E: avoiding certain wording. Nothing substantive.
He sounds extremely abusive.