Even absent a study providing empirical evidence (the OP might not even have been referring to any sort of study, perhaps his comment was meant to reference his personal experience) the statement could still be true. If you are sending primarily one-sentence messages, as many people do in SMS/iMessage/Slack, the line break effectively serves the function of denoting the end of a single sentence. And if that is the case, what is the purpose of a period other than to add additional, perhaps emotional, meaning to the sentence?