I believe WNZ is equipped with tip-tanks also... they can take a wee while to transfer -but not that long. Reasonable aviation practice would dictate that only one engine at a time was transferred to/from the tips anyway -if indeed that has anything at all to do with it.
But even with the tips, a simpler fuel-system is harder to imagine... one tank, one engine. As long as the fuel's there, they'll keep turning & burning.