It was a Rhetorical question, you are losing users because most people wont waste their time when posts are blocked.
They simply leave the forum and dont return.
The forum is fighting against spammers, there are a lot shills here, if the forum didn't have cool down of every post, they can create a bot and start to shill their shitcoins in every sections.
Honestly I don't think 6 minutes is really long, except you're forcing yourself to post as fast as you can.
Back in the days when I was still a newbie, I never experienced a duplicate error message but my post was not there, I guess you're keep clicking to post when you're still in cool down.