Why is the quadrature PA less sensitive to load mismatch?

Could someone please advise why the quadrature PA (balanced PA) is less sensitive to load mismatch? (balanced input/ single output)

Is there any article to elaborate this?

Thanks a lot.

because the reflections end up mostly in a 50 ohm termination.

Sorry could you please elaborate a bit more as I'm not familiar with the architecture of balanced PA?
Thanks for your help.

See http://www.odyseus.nildram.co.uk/RFM...Amplifiers.pdf