Well, it's not always a beginner's question.
Due, I believe, to a left shoulder problem over the last year that seems to include a nerve impingement, my left biceps had actually lost size. I really hadn't noticed it as I don't hit double biceps shots (not that there's anything wrong with that) and for that matter it is hard or sometimes impossible for me to get the left arm in that position anyway. And I was equally strong on the left as on the right in unilateral rowing exercises, and I didn't have any issues I noticed with barbell exercises including EZ-bar curls.
But yet it was so.
Fortunately it hasn't seemed to create an imbalance of other things on the left being thicker than the right, except, oddly, the left upper trap is a bit thicker than the right. But that could be unrelated.
Anyway, my solution to the problem was at first more sets for left than right, but this did not help (perhaps the amount being done in the first place was fairly optimal, as it was intended to be after all); then doing the same as usual for the left but on the right side immediately supersetting a unilateral DB exericse for the left but this helped only a little. Finally I focused on solidly putting mental focus particularly into the left biceps while doing curls. Though this was in fact not more work, it's what fixed the problem, in my case anyway.
For that matter, as for this not necessarily being a beginner's thing, that year that Coleman's right lat was relatively small, he says that was from nerve impingement, and he was not able to correct that within the same year. Imbalance is not necessarily a beginner's problem.