They would fit perfectly, the surface of the chip is perfectly flat, and you put a perfectly plat plate on them -- you get an even contact and perfect heat transfer, so these plates do work, but if your question is "will this solve the main problem with all the 17 series?" then the answer is NO.
As each chip uses solder with the original heatsinks, it would be difficult to get the perfect quantity of solder on each chip so that the custom heatsink would sit level with them all.
However this isn't an issue as I read now the custom heat sinks use a thermal paste instead of solder. Any imperfect plane would be offset by the thermal paste.
As I explained before, the issues of bad soldering between the chips and the hashboard itself can't be solved by using this signal large heatsink, it's not very common for heatsinks to fall apart, if that was the main issue then this design would do the trick, but it's not.
It would be easier to remove a single large plate when you need to fix something underneath it, a lot easier than having to heat and remove a dozen small chips, it may provide slightly better cooling than the stock design, but it certainly isn't going to fix the major problem which is the most common, in my honest opinion the person who invented this large heatsink is a con artist, he knew that many people thought the issue was always in the heatsinks, so "pretend" that you have fixed the problem so you can make a ton of money by giving false hope to miners.
My general advice when it comes to these trash miners is -- don't buy them.
They look like a lot of work to apply, not sure worth the time.
Also, I agree with you these custom heatsinks are likely a double-motivated marketing stunt that don't address the actual problem.
