Is it faster to jump around?

No, it is not faster to jump than to walk ! However is does help to get in the mood !

This kind of behavior is very common for pro players and streamers during startup phase, mostly to keep the attention (of themselves and/or of watchers) on the game. It is boring to wait for the start or to walk to the first objectives, both for the player and the watchers. While this is very important for streamers, this is quite often just a sign of impatience.

In other games, this can have a slightly different form. Like clicking on buildings like crazy in RTS, moving back-and-forth on a MOBA lane, doing on-place 360° in FPS and so on...

I even saw pro players having such behaviors in Hearthstone, a card game with no movements at all.