Fixing decreases on a glove

I just knit a pair of fingerless gloves, and on the first one I only did half the decreases on the thumb gusset. Naturally, I didn’t realize my mistake until I finished the second one and saw how much better it fit. Am I right in thinking that if I want to make them match, I need to frog the first one back to the row where I joined the thumb?

Yep, you could do that.