hmmm. brakes needed for flatland ? simple question, complicated answer.
the current trend is brakeless bikes.
but that trend started at the pro level and worked its way down. so some tricks that used to require brakes are being done by pros brakeless. super hard. (like brakeless multiple whiplashes, or brakeless nosewheelies).
but then there are other tricks that never really required brakes in the first place, and beginners can work on those. like hang 5's, steamrollers, hitchkers, etc.
there will be a ton of things you can work on, regardless of whether you run brakes or not.
you also don't need a new school tiny flatland-exclusive bike to ride flatland. a short-ish street bike, like 20"tt or less, with 4 pegs, will do fine.