Yes and no.

A person with no experience doing distances, but lots of experience riding fast over short distances, could dash down the road on a century at 30 km/h, and be at 60 kms by the 2 hour point ...... but also be in the early stages of bonking because he/she doesn't know how to eat while riding .... and could also be in agony because his/her saddle is wrong and the bicycle is set up wrong .... and thus may have to slow up, or get off the bicycle for a while, or even quit. If this person does finish, there's a good chance this person will be extremely uncomfortable, and may decide never to ride long distances again because they are just too painful.

Meanwhile another person with lots of experience doing distances, but who isn't very fast, could ride casually down the road on a century at 20 km/h, and be at 40 kms at the 2 hour point (way behind the other person), but because that person has experimented with his/her eating, and has his/her bicycle set up correctly, that person could keep going, and going, and going .... and finish feeling quite good.

I've seen it happen ... many times.

This is not to say speed work is completely unimportant. I usually recommend doing something like intervals once a week, and/or riding with someone slightly faster, and/or doing hill work and things like that ... but there are much more important things than speed to help a person finish a century.