It wouldn't necessarily be a story as to how competant he'd be as a president, if it were taken inside a bubble. But let's see what's happened during Bush's tenure.
War with Iraq
Highly Questionable Reasons, Highly Questionable game plan
War with Afghanistan
Justified Reasons, Highly Questionable game plan
Al-Qaeda
Justified Reasons, Highly Questionable game plan
There are many questions about his leadership as commander in chief during this presidency, and the results of his leadership. If it turns out that he ducked his service in the military, then it just adds to that very real perception that he is unfit for the job and should not be re-elected.
In and of itself it would not necessarily be a story. Tied in with everything else swirling around the White House, and it adds to the shark bait.
That is why it is more relevant today, politically, than it was in 2000 or 1994. Especially since you're potentially contrasting his military service with someone who actually served in Vietnam and came home with a chestful of medals, vs Al Gore.