I don't think people are suggesting that, quite the opposite. They're saying that tournament Jiu Jitsu should have good crossover to real fighting so that we're not left with just a bunch of TMA-ish drills as the "self defence" part of the style.
Coming from a judo-wrestling background, I'd argue that a lot of the crossover comes from being in good shape and being used to the aggression and mechanics of grappling, rather than cross overs in the techniques themselves. Lots of wrestlers, with no cross training in BJJ or MMA, have done very well in armed street encounters simply by being fitter and more used to the mechanics of grappling, because most people you might attack you on the street unarmed aren't serious fighters (serious fighters in a street situation use weapons and numbers - ask any cop).
You even get this with throws and takedowns - the way they're drilled is often very different than what happens in competition, because an adapting, resisting opponent changes everything.
Which suggests that problems in terms of self-defense come not from banning or limiting individual techniques, but from not allowing a general category (ie grappling arts lack striking, wrestling lacks submissions, judo is starting to lack ne-waza :icon_sad:, striking arts lack grappling). So long as the equivalent of full contact sparring is a large part of the style, it'll suffice for low key self-defense situations, which tend to mainly be against untrained people.
That was in fact Kano's whole point when he started judo. Traditional Japanese ju-jitsu's had a lot of very effective techniques that were banned in judo because they couldn't be safely used in randori (sparring). However, many would argue that the judo route (being able to go full out with a reduced set of techniques) is actually more effective for defense than having a broader set of techniques that can't be safely practiced in full out sparring.
I'd rather have a good sport BJJ'er covering my back in a back alley than someone who's spent a lot of time practicing self-defense BJJ instead of actually perfecting their mechanics in rolling.