Those aren't exactly unopened buds. They are fertile flowers (the big showy ones are sterile florets) that all hydangeas have, some much more than.others. Fire & Ice tends to have not very dense panicles and with a lot of fertile flowers so yours is close to what it should look like, although you may well get more of the sterile flowers opening as the season progresses and as the plant matures. The fertile flowers tend to be tiny compared with the sterile ones and often like like they are unopened.

waiting game.

The flower buds are normally invisible and resemble little broccoli heads when they open. Then they form these panicle-shaped blooms.

Thank you all! This is very helpful! :)