I second that. The problem is even worse because the ancestors of that grandparent who shows up as a cousin will become parents/grandparents of the spouse of ___ cousin and just gets worse and worse as you add ancestors, that is if you remember that they are your ancestors and work on them instead of going by the relationship in the corner and thinking they are just cousins and skip them. Another issue, is that the software becomes less responsive when trying to enter information on those ancestors. How sluggish seems to be related to their relationship designation and the size of your file, but with a really large file some can be so sluggish it becomes too time consuming waiting for the software to catch up every time you try to add details to that person.
Even if you haven't personally encountered this problem yet, it would be helpful for you to also report this issue so that they will fix it before it does start happening to you too.