VO2 can be measured walking and running (according to my Vivosport device). But in the Connect Mobile app (and in de Connect webpage) you can view the VO2 results for "fietsen" (=cycling). Seems to me a translation error.
And just to clarify even further, cycling VO2max cannot be measured by your vivosport, because a bike power meter is required for that, and the vivosport does not support power meters. So for you it's only running VO2max, which can be calculated either by running or walking.