Here is a drawing of the two:
The circular 8 is much more common than the square "shape" that kind of could be considered an 8 on the right.
I would like to know why.
In both shapes there are clearly two "divisions", and they both have the same "orientation". So it seems they should be both equally 8. They also don't really conflict with any other shape I don't think, well maybe
0 a little bit.