The TR requirement is a tactical decision to get bums on seats quickly.
Strategically, BA want the right people aboard for their 30, 40 year careers. Entry TR is therefore largely an irrelevancy.
Billions of hours on the "right" type will mean little once the immediate requirement is met - it'll revert to the BA merit basis, taking the right raw material and leveraging one of the most respected training infrastructures.
Welcome back opportunities for SSP and FlyBe guys.