This happened to me too, but in snapshot 17w50a, but instead of using the texture nbt, I used the SkullOwner with the player name like this : {SkullOwner:"PlayerName"}.
Don't be confused with the total darkness bug when Blindness + Night Vision are combined, I am referring that when you have these effects on the latest snapshot (17w50a) and go underwater, there's an overlap effect with the water texture and the darkness. Thanks
It's intentional, you need to use /execute as @p at @s run function <namespace>:<function>