Like if there were 2 people with the same bicep size, would the one who also worked on the small muscles be stronger?

I don't know if that makes sense.

There was this class for women that focused on small arm muscles to tighten up their arms instead of
bulking them up

If you work on the small muscles of the arm, you will be stronger in performing the movements controlled by those muscles. For instance, if you work the brachioradialis muscle (near the bicep), you will be stronger in the final stages of elbow flexion, and in the movement or rotating the forearm. The larger bicep muscle provides the force to flex the elbow along most of its range of motion. Modern physical training methods work to include all the muscles in the area being developed, so the musculature will be balanced and full range of motion will be preserved. The stories of overdeveloped muscle men who are "muscle-bound" are examples of unbalanced development of one group of muscles at the expense of others.

Muscular development classes for women often focus on lower weights because large increases in mass are not desired. Also, lower weights with higher reps will train the muscle more for stamina and definition, and will add muscle tissue that doesn't take up as much space. Working on the small muscles in the class was probably just part of the approach of making sure that the development was balanced.

tht class if probly more for making them look lean and not actual stregth