Leaving aside the facts of Phillipson’s upbringing, such as they can be proved, I agree that a personal appeal on the basis of shortage, or riches, or special circumstance is off-putting.
I don’t think the worse of Starmer or Davey for being obviously middle-class, or think more highly of Badenoch for being a black woman. Although, to be frank, she has much the best claim of any of the leaders to having overcome social barriers.
Starmer is probably the worst Walter Mitty for being so coy about the truth of his company-owning dad’s background, his schooling, his flute lessons at the Guildhall and all the rest of it.