Odds are they did. Some version of this is a pretty common house style that the first reference to the president they say "President Obama" or "President Barack Obama" and then after that say "Mr. Obama" or just "Obama."
NPR got slammed for this last year by people certain that it was a sign of disrespect, something they'd never have done to a previous president and they did a demonstration of them using the same style through many administrations.
So can't say it is true of everybody who is saying Mr. Obama that they did the same to Mr. Bush but it isn't at all unlikely.
As another example, it is the house style of the San Francisco Chronicle that on first reference they say "President X" but then on subsequent references they just say "X".
Here they do it to Bill Clinton.
Here they do it it George Bush. Here they do it to
Obama.
The problem with it on TV is that over the course of a story you'll hear "President X" just once but "X" or "Mr. X" many times and forget you heard the first one.
(And also, of course, opinion shows probably don't have to meet house style to the same degree so it's probably laxer there with people talking in a more natural way; and opinion shows are more common than they used to be.)