Ah yea… there’s a trick to it 
You have to create the static page FIRST. Then create your collection slug with the same name. That get’s you past that validation error and allows you to successfully do it.
Here’s an example:
I took this approach for the example above.
Here’s the project share link to see it in action. If you already have a collection with the name you want, you’ll have to do a little renaming dance, but it won’t be bad 