Have had some toons with a lot more rested then others, at the start of an expansion.
Not sure if this was ever fixed, with rested capping.

I seem to remember having just a couple of bubbles on some.
And more then a level on others, when starting Burning Crusade.

But don't think I had much initial rested, with WotLK on any toons.
Might have just raced to 70th on each team, and dinged with very little rested, not sure on that.