What you're seeing are the speeds of various multi-tier caches (RAM, intermediate SLC etc.) It cannot write to its main flash memory that fast. While it to the user looks like they just wrote 10 GiB in a single second, the SSD is internally still busy for another 10 seconds persisting that data. The actual real write speed of top-shelf consumer grade SSDs these days is somewhere in the vicinity of 1.5 GiB/s. Most models top out at half of that or less.
I bought this one when upgrading my desktop, it indeed delivers what it promises. 14.5GB/s on my tiny random desktop, it's impressive. Everything feels so instantaneous, my Linux desktop finally feels like a Mac :)
That's certainly impossible as even USB4 is only 40Gb/s~5GB/s, and of that you could only expect to get 32Gb/s~4GB/s. Or realistically even less due to overhead.
It is probably the speed of it being read into RAM.
Try entering sync right after copying to see how long it really takes
