Well that's just it, flaring is open burning "waste" gas, which doesn't provide complete combustion, enclosed combusters operate at much higher temperatures and burn off more of that methane... So they aren't just covering up their flaring - they're complying.

And yet - 'Former regulator at Texas CEQ said: “Enclosed flaring is, in truth, probably less efficient than a typical flare. It’s better than venting, but going from a flare to an enclosed flare or a vapour combustor is not an improvement in reducing emissions.”'