With juniors Tim would pretty much be training them and nudging them on to write better code.
With seniors, like the short article says, it’s more a sparring match, trying to find the best solution. You also find a lot of edge cases when someone else works with you together.
I haven’t been in a company yet where they have a full time floating position for pair programming, but if it’s a senior doing it I can see how it’s very beneficial for product quality.