I think he means it the same way as when they say you should use a reference track sometimes.
I had (and still have at times) a lot of trouble with loosing myself in the sound when listening for a long time to it. So same thing, if you are working on a song that is your own, you can get lost in to it. If you know what you need to hear, you can hear it better then some one who doesn’t know. So maybe “imbalance” isn’t obvious to you at that point.
Even for free, you should suggest a contest for this. I think enough people would give it a go, even for the prestige alone Its still practice for any one, how good he already is. Especially to overcome the “issues” discussed here.
@holster Your thoughts ?