EDIT: Discovered that Mincraft generates "cave air", so there's no bug.

Example Location:

Seed: 1497405538277912123 at X:-288 Y:12 Z:300

I ran this command and it failed to set glass blocks:

/fill -228 11 300 -238 15 290 minecraft:glass replace air

I could also run around this box room and use:

/execute as @s at @s if block ~ ~ ~ minecraft:air run say hi

and nothing would happen.