Rule 8.9 for Football can cause some confusion, because it specifically mentions omni wheels.
It was written this way because almost all robot designs use omni wheels. But the intention of the rule is that each robot can have a maximum of three driven wheels in total.
Therefore the rule should be read as follows:
8.9 A maximum of three driven wheels – built of only LEGO branded components – can be used on a single robot. Use of a reciprocating kicker in the remaining EV3 output port is strongly recommended.