I think that's just how they've implemented the notification light when charging. I've seen someone on another thread about this say theirs was blinking when charging but I've never seen it blink and I don't think he was right on that.
What phones do blink when charging? I've always had HTC devices and they've had it set up like this for all the time I remember. I've never minded since I don't want to be staring at my phone all the time to decide whether I have any notifications. I just listen for audible ones 90% of the time.