Update: my 3x5 balcony jalapeño gave me 14 peppers and I looked up why
I always figured balcony peppers stay tiny since the pot limits the roots, but a master gardener at the Portland nursery told me last Saturday that small pots actually stress peppers into fruiting early. Mine is in a 2 gallon fabric pot on a south railing and it's outproduced the big raised bed I had at my old place. Never would've bet on that. Anyone else notice their cramped plants doing better than the roomy ones?
My buddy grows habaneros in old cat litter buckets on his fire escape and those things go nuts every single year. He tried moving them to nice big 10 gallon pots last summer and got way less fruit, just huge leafy bushes with barely any peppers. He read somewhere that when the roots hit the walls the plant panics and starts making seeds fast, which makes total sense with what that gardener told you. Now he keeps everything root bound on purpose and swears by it. Your 14 peppers off one balcony plant is seriously impressive, that fabric pot is probably air pruning the roots too which helps even more.