The bug

On Fabulous, you can see transparent blocks like water, stained glass, etc., and particles, clouds behind semi-transparent armor stands that are not markers, but when it is a marker armor stand, you cannot see water, stained glass, and other transparent things behind it, even on Fabulous.

How to reproduce:

1. Switch to Fabulous!

2. /summon armor_stand ~ ~ ~ {Invisible:1b}

3. Summon an invisible marker armor stand near it using

   /summon armor_stand ~ ~ ~ {Invisible:1b,Marker:1b}

4. Go into spectator mode
   You can see water, etc. through the non-marker armor stand, but not through the marker armor stand.