my brother came up with a great analogy - say you’re falling and there’s a portal below you also falling, just slightly slower than you. when you eventually fall through it - do you come out falling slowly or quickly?
it would have the be quickly. even though you and portal are moving slowly relatively to each other, your individual momentum is conserved, the movement of the portal is irrelevant.
in my interpretation of how portals work - by joining space together - moving through a portal doesn’t involve infinite speed because you haven’t moved - the portals have just changed the space you occupy.
a bit like the inertialess/ Alcubierre drive where you travel faster than light without breaking any laws because you’re not moving at all in your space, it’s just that the space you occupy changes.
in the reasoning the people hurling towards the portal only appear to do so, once they pass through the portal they’ll be as immobile as they were before entering it.
the minute physics video is fun though. love their stuff.