If I recall correctly (and I might not), they change aim once before ramming you. Therefore, you need a bit of extra space between yourself and their initial target.

If that's not it, there's still some reason why I do that. Yes, they aim at the ground, but maybe every once in a while tanks killed me by shooting my feet, and that last little trick eliminated that from happening.
I LOOOOOOVE Flying Omelette!!
Crawl and 1000