Fictional stories are known as fiction. Factual stories are either factual or usually based on something true that may have developed over time.
It’s a valid point that the talmidim of the maharal should be expected to have mentioned something, especially when the tosfos yom tov spends time describing his rebbe, so it’s hard to attribute it to others reasons, such as missing writings etc..
On the other hand, klal yisroel has adopted this story – when we start dismissing such traditions out of hand, we are on a slippery slope… Of course some people here are already on the bottom of that slope, but that’s another discussion that is far more important than whether or not the maharal actually made a golem. For me it makes almost no difference if he did or not, but the impulse towards rationalism and the attempt to remove the spiritual from our history is the truly scary thing