Yes, according to your data this looks like only around 5% of the total merit transactions face such merit double sending problems approximately
I agree by looking at the numbers it is not that big of an issue and most of the generous merit sender's would not do such double spending mistakes often.
And some of these will be intentional. I've merited a post, and thought "actually this probably deserves a little more", and have then proceeded to reward more merit. In the grand scheme of things this really isn't a problem, and only affects such a small amount of users.