Just let the poor kid ride his damn skateboard god damn.
If you
must extract meaning from it, it means he was a tiny bit athletic already and had good balance. Traits that would come in useful when he got super powers and used them in ways that required exceptional balance and coordination. The
brief sequence also set up a location he later used to train in (rather than skateboard in) while swinging from chains and generally being gymnastical (that's a word now).
While we're on the topic, why the fuck did Peter's hair look like that? All big and flaired out like that. What does that say about his character? What did it
mean? What's he trying to prove with big hair like that? Is he trying to show off? Could this have deep existential meaning relating to his feelings of inadequacy stemming from deeper feelings of abandonment? Is Peter's hair really his father's fault? And following that line of thought, could we blame his hair on the man responsible for that,
Norman Osborn?