<target> not working

when using

/execute as @a[x=0,y=0,z=0] positioned 0 0 0 run gamemode a @a[x=0,y=0,z=0]
or
/execute as @a[x=0,y=0,z=0] run gamemode a @a[x=0,y=0,z=0]
or
/execute as @a run gamemode a @a[x=0,y=0,z=0]
or
/gamemode a @a[x=0,y=0,z=0]

result:

turns all players at all locations into adventure mode regardless of anyone's coordinates.

desired result:

only change gamemode of players at coordinates 0 0 0 to adventure