There are different types of fiber out there in the wild. Yes the physical cable is the same but deployment is different. There is shared fiber that will say speeds are “up to” such as Google and municiple fiber and then there is dedicated which is guaranteed. Dedicated will come with service level agreements. That’s why you can see different pricing for different fiber services. Shared fiber might be amazing for a time but will eventually get oversubscribed and start to vary more usually because the provider is borrowing the network. They need to get a certain number of customers before they can borrow more bandwidth which usually doesn’t happen. These networks usually don’t get upgraded over time