I don't see the problem. Jargon often uses words in ways different than "standard" English. The language is fluid and words mean what speakers and listeners take them to mean.

I doubt there's anybody who doesn't know what's meant by "geometry" in the context of bicycle frames. In all fairness it's not a bad choice of words anyway, since we're talking about lines and angles.

IMO- "dimensions" in this context is a bit too limiting since many don't include angles when they think dimensions.