It seems like am more user friendly version of the adjustable gas key.
I still prefer systems like the Noveske switch block or adjustable systems found on Adams Arms.
Similar concept, but really meant for different purposes. The adjustable gas key and adjustable gas block are really designed to "tune" the gun to run on as little gas as possible while still providing reliable cycling. They've been around for years in the competition market and recently adapted to low profile gas blocks for the Tactical crowd. Because, profit. They can be useful on barrels that have an excessive gas port size though. This was really more of a problem when carbine gas systems were more dominant and short barrels were less prevalent. Adjustable gas block and keys aren't friendly for suppressor use mainly because you have to count clicks on the block or count fractions of a turn on the key.
The switchable bolt carrier is more akin to a switchblock. It's either wide open or restricted. WAR uppers fall in the same category. These days, with better gas port sizing, enhanced carriers (LMT), A5 buffer systems, etc, a gun can easily be tuned for reliable suppressed & unsuppressed shooting without having to switch anything on or off or disassembling the gun. Theoretically, they might help with gas face, but that's just theory. I don't think they really make a huge difference, since the only time I ever really notice it is shooting indoors, which I rarely do. I've found that retarding unlocking of the bolt is just as effective and doesn't require me to turn anything on or off. It also makes for a very soft shooting, reliable gun.
With all that being said, I'd prefer that gas flow be restricted at the port, rather than at the gas key, either by an adjustable block or switchblock. I don't have quantifiable data, but it seems to me that restricting all that pressure at the carrier may create a more harsh unlocking and greater wear on parts or early failure. Just my theory though.
The gemtech carrier seems like a specific solution for a specific problem. But it won't be marketed that way. Again, because profit. The most useful scenario I could see this being used would be a drop in solution for an overgassed, suppressed carbine, when swapping other parts isn't a viable option due to cost, departmental requirements or supply chain issues. ie: LEO or military use on issued carbines with carbine gas and a barrel 14.5" or longer.