It’s not exactly radically different from how RAM typically works on any standard PC, especially now that the northbridge functions have mostly been merged into the CPU on most AMD and Intel options.
The only real problem is it isnt standard, if socketed NAND of that form factor and controllers in the CPU/SoC were standard this wouldnt be an issue at all
And when an update is down loading the time of 1 minute 59 seconds is "about" 1 minute in Apple terminology. So "about" 2 years could be anything up to 2 years 364 days. I hope it isn't that long, I hasten to add, but Apple's "about" can be a bit misleading.
But the thing people are missing, post house’s and facilities these machines excel in don’t upgrade and purchase like consumers do. It goes through finance and planning and takes a while to be approved and budgets for the year. They don’t just spend money when new systems launch. They often run them for years and years.