That's rather irrelevant. The point is that Hull Down makes your tanks immobile in a game that is dominated by manoeuvre warfare. You're going to lose the initiative and you're going to be dependant on your enemy if you dig in all your tanks. Which can work well often enough if your opponents charge headstrong into your lines, but if your opponents are good they'll just go elsewhere and overrun some other part of the map or wait until they have offmaps available.
Because we all know you can only hulldown all your tanks together or none. Beside thta those comments remember me some other made long time ago to defend brit simcity.