I tried it in both last night and it worked from both. There is a ‘save’ button IIRC on the tray tool that you have to click to actually apply it.
Also, it’s very weird that this is doing anything – the FOV multiplier is only supposed to affect the mirrored display on the 2D desktop monitor. The same is true of the FOV stencil. The fact that these are showing up in the HMD is almost certainly a bug in the Oculus software driving it. A useful bug but a bug nonetheless. I suspect this is due to the way Link is capturing the image, and I doubt it works for Rift S or CV1 but will test when I have time today. It definitely won’t work for non-Oculus devices, though. That FOV multiplier is part of the Oculus runtime; it isn’t present for anything else.