Unless I'm missing something: Huh? Apple is just using regular NVMe/M.2 SSDs, nothing special about them. Lots of laptops have the option for M.2 NVMe SSDs, and most newer desktop motherboards have the slot for it.
Just as a sticking point, Apple's SSDs are not, and have never been, regular NVMe or M.2. They have always used their own stupid custom proprietary connector, despite basically implementing most of the relevant standard (NVMe/PCIe/SATA).
A lot of laptops that advertise NVMe SSDs are using inferior TLC-based or non-Samsung SSDs to check that box. Apple's not alone at the top (especially when aftermarket upgrades are taken into account), but they have been pretty good about using the fastest PCIe SSD that money could buy at the time of release.
True, but I don't think that's common near the price point of Apple hardware.
It's also not uncommon in the "lower ranks". I just bought a 800 € ultrabook with a 256 GB Samsung PM961 SSD (NVMe, 2.8 / 1.1 GB/s) and the Skylake i7 for example.
Also, don't forget that one can buy a Samsung 960 Pro in a machine that comes with a cheaper SSD but uses a standard M.2 NVMe slot, and ditch the original SSD, for cheaper than any of Apple's capacity upgrades.
The Samsung PM961 is not top of the line. It's one of the more recent TLC-based alternatives that shares a controller with the top of the line products, but it's inherently slower and less power efficient.
Specs seem to be 3.1 GB/s read and 2.1 GB/s write speed. While that's faster than most M.2 SSDs, equally-or-better specced SSDs are already on the market, eg. Samsung 960 Pro (3.5 / 2.1 GB/s).
