I think the warped spacebar issue might be extremely over exaggerated. I have opened like 10 gmk sets in the past year and have not run into any issues with the spacebar being warped and I only use the 7u one, it is also possible that it is just extremely rare. The people posting about it could be attributing issues with their stabilizer or switch to a "warped spacebar". Aesthetically I also don't believe you would be able to see these slight warps when it is on a keyboard.

When people have any issue with something as expensive as this they are going to be really loud about it and it will gain a lot of visibility, rightfully so, but you and the commenter two comments up have to consider that this creates a bias that makes it look like everyone is having problems with gmk when really almost no one is.