For what it's worth, I compared the files in Ankor's 01/17/2018 shaders to the 12/04/2019 (latest) ones (after removing the readmes and other non-functionals):
2018
4 folders
100 files
2019
7 folders
72 files
Unique to 2018:
Effects\fxtextures\59 reticle files (reticle.mkii_bar.dds through reticle_ussr_mig.dds) and tr_condenstrail_basis1.dds & tr_condenstrail_basis2.dds
Effects\weather\7 sun files (sun.dds through sun_main.dds)
Unique in 2019:
d3d8.controls.txt
d3d8.pointers
shaders30\common.commands.ini
shaders30\common.functions.ini
shaders30\cursors\green\17 cursor files (CursorClick.cur through CursorScroll.cur)
shaders30\cursors\white\17 cursor files (CursorClick.cur through CursorScroll.cur)
shaders30\demo\spitfire_ixc.clickable.ini and SpitfireIXc-Demo-Starter.ahk
I'm a complete amateur at this sort of investigation, but as my 'trick' involves 2019 overwriting 2018, I'd suspect that the answer lies in interactions with files unique to the 2018 ones? There isn't even an effects\weather folder in the 2019 ones.