I didn't ask specifically, but the most probable reason for this is that the Xbox Live libraries used for achievements on the Windows Store are only available for 2017 and later. Class layouts are unlikely to change, luckily.
This changes the way that the code is generated in a way that forces mod developers to start from scratch finding functions and writing hooks. The reason for this is that as part of the AE update, Bethesda has decided to update the compiler used to build the 64-bit version of Skyrim from Visual Studio 2015 to Visual Studio 2019. With the AE update, all of these methods will break, and addresses will need to be found again from scratch. SKSE uses an offline tool I developed a long time ago based around position independent code hashing. Other plugins use code signature matching, which finds functions that 'look like' a specific pattern. Most plugins use the Address Library by meh321.
During that time, code has been developed to make many plugins portable across different versions of the game.
The native code modding scene around Skyrim SE will have been around for about four years when AE comes out.
