Format Y - H is the same of Y-8 format but requires an hypercardioid mic instead of a figure 8 for the surround channel. Even if the placement is similar the 2 techniques have different encoding settings and they are very different.

Purpose: The Y format provides 4 channel of Surround encoding on 360° degrees.
The directionality of the hyper 8 is used for dominance in the mono surround channel.
The good rejection at 270° creates a better psychoacoustic acceleration on the surround channel.
On the Field X-Mat you address L and R mic on L and R channel on phase and on bus 3 at 1/4 to 1/2 respect to bus 1 and 2.

Input 3 and 4 are linked out of phase and at 1/4 level more comparing L and R.

-Advantages: Stereo encoding (DAT etc.)

-Compatibilty: Stereo and around 1/2 of the level in mono for the surround channel on axis. Good 5.1 ready to encode.

-Disadvantages: Little lossy of the surround image in mono. You may anyway compensate in post pro.

Position: The same as format Y-8