Either I am dump or there is something missing/ there is a bug at the new NBT tags of potions. You can't use them at for example "/scoreboard players tag" to only tag a defined potion, like night-vision. I found nothing on the Internet explaining this and no other Issue dealing with this.
Example:
/scoreboard players tag @e[type=Item] add Potion {Item:{id:minecraft:potion,Potion:"minecraft:night_vision"}}
I tried every other combination, like
{Item:

,Potion:"minecraft:night_vision"}
but nothing worked.
(If I just used the wrong NBTs, I excuse for creating this Issue, but I didnt find any others. I think they are the right, because they are used at /give and every others are unified, too)