Please find the source of where it was promised, because this is the first i've even heard any complaints about it.

It doesn't exactly fall under good interface design, I just don't personally find it disruptive. I've never had to look at my macro bar and read what's in the first slots while casting a spell. This is mage jobs we're talking about, not melee, and I've never had an issue. I'm not against fixing it, it's just not important.