Not serious design flaw la. I believe they added that to solve sound buffeting sound which is apparent as our head level is same on window.

Then he went over to CRV which had all round seal. As the car was sold as higher range, it require more seals for NVH.

Its acceptable la. for that dirt annoyance, unless you somehow managed to get a rock stuck inside thats another story. They could choose to crimp seal the top. but c'mon.... this is budget range car, they won;t spend the extra to do that. If you use silicone to cover the hole, it would harden and cause other problems.