I would add that in going from a 550MBps SSD to a 3500MBps Samsung NVMe, in day to day stuff...I cannot tell the difference. There is a limit to the speed benefits. But cheaper and bigger is always nice.
You are absolutely correct.
If your goal is starting a game then games in general don't really load much data to start.
They load alot of small files that need to be processed by the cpu.
Tom's had an article a few years ago that illustrates this beautifully.
629 megabytes of data needed for Civ5 to start.
Civilization V took 38 seconds to launch but of those 38 seconds the ssd was only busy for 2.15 seconds
Note they used a Sata based ssd, OCZ Vertex 3 240 GB.
With a 3500MBps Samsung NVMe, assuming 960 Pro, the game start time would not be affected by much if any.
The disk busy time would only be 1 second or less followed by 30+ more seconds of waiting for the cpu to catch up.
The only way to really see the difference would be to transfer a multi-gigabyte file between 2 ssd through an interface with a higher than 540 megabytes a second bandwidth, like 10 gigabit ethernet.
540 megabytes a second being the read speed of an 850 Pro.
10 gigabit (1.25 gigabytes a second) would be about 50% saturated from a sata based ssd, like an 850 Pro.
Due to the 10 gigabit limit a Samsung 960 Pro would only appear to be twice as fast as an 850 Pro due to completely saturating the 10 gigabit link.