I also see students, particularly kids, with stripes and buttons on their belt between grades. And "pre-black belt" steps after attaining 1st Gup. If they have to pay for each of these then yes, I think that is a McDojo. I do agree with a Po Dan signification for 1st Dan students under 16 years of age.
The stripes look shabby, but they can be great way to help kids track their own progress (and for us to see where they're at). We started using them a year or two ago, and it makes things so much easier.
What we do is we have a color stripe for each major element of the curriculum. They earn each stripe by demonstrating good competence of that specific material in class (the stripe is awarded at the end of the class, and doesn't cost anything). Once they have all the stripes, they're eligible to test at the next testing date.
I don't think it's unreasonable to have a "pre-test" for black belt, either, but that's up to the school and what they want to do.