For Call of Duty, specifically the Modern Warfare reboot they went back to doing forward rendering and added tiled light culling so their gains make perfect sense but they use a software implementation of variable shading regardless so no platforms are left out of this benefit. On Metro Exodus EE, from
this single data point the gains for VRS amounts to maybe 1 or 2 more frames which ultimately doesn't mean much in the grand scheme of things ...
As for the Gears games, I don't know exactly what the register pressure of their shaders look like but if they are struggling then they could potentially see some benefits ...
As we go on further on into this new generation, the proposition for VRS becomes a lot weaker as most developers will likely continue to use deferred rendering. It becomes harder to justify using the technique when games are also going to increase geometric density in the future ...