We had no dismissal when I attended RCIA - there were too few of us, and it was too hard on our sponsors to miss communion, leave their families, and them have to hunt down another service. We only had one instructor and an occasional volunteer (not often).
Matter of fact, we’ve attended many churches over the years, and we have yet to find one that did Dismissal for RCIA! Mostly, RCIA met one night a week at the rectory or community room for instruction. We were told of the concept of Dismissal, but informed that it wouldn’t work and to just stay in the pew or come up for a blessing.
Our current church is so tiny that the RCIA is only taught by the Priest, so since he can’t leave the altar to accompany the candidates out, they all just stay and come up for blessings. The candidates meet with the Priest weekly at the rectory.
Dismissal is a lovely concept and a nice throw-back to our history, but it is not always practical in some areas.