It generally makes sense that the best server should serve first. Often the first guy will end up having to serve one extra game compared to his partner. The first server in the set will also serve first in the tiebreak, which is important.
That said, there are a bunch of different factors that could change this. For example, being opposite-handed, the Woodies used to pick their ends depending on the time of day and the way the court was oriented. Woodbridge was the better server, but he'd often go second if it meant neither of them had to look into the sun whilst serving.
Who knows. Perhaps Moser was overhitting the ball too much, and they swapped over to give him a chance to serve into the breeze. Little things count.
Really, it could have been a million things. Bit rough of the commentators to criticise, IMO.