This is good advice. I used to help maintain a bit on the bigger size project on Github and our lead developer I think really wanted to spend time looking over and trying to give quality responses. Which ended up sometimes taking a long time or not at all. Unfortunately, it came off to some people as not caring about their submissions. Just a simple message about being busy and asking them to remind you if you forget works wonders.

Example: "Thanks for sending this in. I'm busy right now but will look into it later. If I haven't responded in a week or two, do me a favor and ping this thread."