Ofcom haven't ruled Wikipedia is Category 1. They haven't announced the intention to rule it Category 1. The Category 1 rules are not yet in effect and aren't even finalised. They aren't pointing any gun.
Wikipedia have a case that they shouldn't be Category 1 if that happens. But they went fishing in advance (or to use an alternative metaphor, they got out over their skis).
What else is the court to do but give a reassurance that the process will absolutely be amenable to review if the hypothetical circumstance comes to pass? That is what the section you are quoted says.
First, it's a statutory instrument that ministers will amend if it has unintended, severe consequences.
Second, the rules in question have not been written yet and they are being written in conjunction with industry (which will include Wikipedia). Because Ofcom is an industry self-regulation body.