It’s not that the highs aren’t there, it’s just a crispness that’s different and may be a characteristic of class-D
I think it could be explained better that the highs from the Pass XA30.5 would wash over you with it’s detailed sound without drawing attention to it self, rather than being fired directly at you from the tweeters with the Class-D. One makes the tweeters disappear the other doesn’t. That’s what linear Class-A does when it’s doing it right. .
Good to see it worked out, like Almarg and I both said you must have had either a faulty XA30.5 or it was something in the setup.