Yes, this mix does have a few missing or altered parts relative to the stereo mix, but nothing deal-breaking, or glaring as you will find on, for instance, the Moody Blues' DAYS OF FUTURE PASSED, which barely had enough multitracks to concoct a quad mix (some tracks are missing overdubs, but you have to be a real fan of the album to catch those).
This is one of my favorite quad albums, if only because it's more episodic and nicely meandering in scope compared to DSOTM, which, let's face it, is a fun listen but has those 'noisy' spots that can grate under repeated listening, whereas WYWH is more contemplative; the playing is relaxed and measured, stretched out to create a unique atmopshere. And when it is a bit wild--WTTM, for example--the mix is so good it's a fun kind of excess, like listening to Keith Emerson roaming around the room in BRAIN SALAD.
Given the complexity of a recording like this one, it's kinda surprising we don't notice more 'errors' of addition or omission, or things out of balance. In the end, it's a great mix faithful to the stereo version, but the quad gives the album a depth of field it needs.
ED