The DocMonitor v2.2 plugin appears to have been released in 2008 (fourteen years ago!) and hasn’t been updated since. Given that it was by Don, I assume that at the time (that predates my Notepad++ usage), he still hadn’t incorporated the monitoring feature yet (file status auto-detection was added in v5.7 in 2010, and full Monitoring mode was added in v6.9.2 in 2016)
Given all the changes that have happened to Notepad++ since 2008 (v5.1), I would say it’s a much better idea to use the built-in feature, not a plugin that hasn’t been updated in one-and-a-half decades.