"9999999999999999999999999999999999999999999999999999999999999999999999999999999 99" seed gives the same address, it's another proof of exclusive status of "9". 
I also noticed that appending 9 at the end of a string generates the same address as the string itself.
isn't that kind of clear, if its considered as a zero/null value? if you prepend it, its not the same, but if you append it is