The purpose of PMQs is to ensure accountability. While there are some planted questions, he must be briefed to answer questions on anything which is current. This is A Good Thing. Indeed, one of the first abuses of Parliament perpetrated by the Dear Leader in 1997 was to have PMQs only once a week instead of twice.

However "responding to questions from the public via YouTube" really means having his flunkies carefully hand pick a sample of questions to which he can respond with some uplifting on-message response. I'm sure whoever thought this up will get a knighthood.