The lesson is about using y in affirmative commands. On y va is not an affirmative command in the grammatic sense.

Hi Ellie,

In my experience "allez-y" and "va-y" would mean "go" (there) -- in the impératif mood.

But "Are we going" --> on y va ? --> "let's go" or allons y (perhaps some element of impatience)

Hope this helps.

Bonne journée

Jim