34mm tube ffp scopes focusing down to 10 yards?

When people say a scope focuses at 10yds, what do they mean exactly?

I would imagine they mean it will focus down to 10yds at all zoom levels. Because while the March scopes say they focus down to 10yds, at most zoom levels they'll focus a good deal closer than that.
You are correct in what you are thinking. The parallax focus feature is advertised at all power levels. The scopes that only focus parallax down to say 25 yards will usually focus in clearly (to remove parallax error) at a closer than advertised yardage, but at a much lower power. Keep in mind that if you are consistently aligned directly behind the scope then there is no parallax error, unless it is a mechanical error within the scope.