This post is about stopping the scammers on Open Mic, not about whether vocalists are musicians or not. I don't know why you keep going back to that in your comments.
We are in agreement. This rule is going to stop scammers, not stop vocalists.
I used that video as an example of what would be acceptable to illustrate that singing quality has nothing to do with whether an entry is valid or not. Obviously he is singing bad on purpose, that's why I chose this video to show an example of an exception and to make it clear that someone's singing ability has nothing to do with this.
It's about stopping scammers. Almost all of the scam entries are scamming the contest by entering acapella or karaoke entries.
This rule will stop scammers, not vocalist
That's why there are exceptions.
Here is another example of an exception.
Steemit Open Mic Week 67 De Una Capital A Otra Cancion Original --- by @ovweedb
Is this a karaoke entry? Technically, yes.
Is it a valid entry? Yes. There is no scamming going on here. These people are really singing this. A scammer would be lip syncing to it.
I hope that makes why this rule is here more clear. If you only knew the sheer numbers of people trying to scam this contest right now you would see why we had to do this.
But the example above would get upvoted for sure even though it is technically a karaoke entry, it is clearly not scam or someone trying to cheat the contest which is what this whole post is about.