Part of the problem is that MG are trying to pretend this is a lesser problem than it really is. Only counting cars where issue is reported by owners, where the (discreditted) re-fill to a lower level bodge has also failed, results in an under-estimation. If MG wanted to be pro-active they could check all their demonstrators and owners cars when in for any work, or contact owners and invite them to return for inspection or ask them to check.
Even if they have not experienced a leak yet, it seems highly probable that most cars will develop one after more time, higher mileage or changes to usage pattern. Getting MG to remedy the problem a year or two down the line, especially by a second owner might become difficult. In the meantime transmission may be damaged due to insufficient lubrication, driveways may be damaged and other users may lose cohesion.
MG have had sufficient time to evaluate the issue and should now be either demonstrating that it isn't a problem, or should be delivering a plan to remedy the issue for ALL vehicles.