[logback-user] Why is modification time of log file important?

Hi everyone, I have a question about the meaning of checking modification time of log file before deleting it. I configured hourly based log appender. Some times, there are no logs appended for more than an hour. In this case, the gap between time in an archived file name and the file's modification time is more than an hour. Which means the file will remain forever until user delete it manually. Is it intended behavior? Why should it check modification time of log file before deleting it? Thanks