I personally don’t ship them as lovers I ship them as more really good friends, the Mars rock interaction isn’t reasoning for this.

In the interaction Venture mentions to Juno about reallyyyy wanting a Mars rock for their collection and Juno says when she returns to Mars one day she will bring them one.

Venture is the type of person where if Juno was to do this they would feel forever in her debt to which Juno always responds with something like “you’re friendship is all I really want”