@s is not Selecting Current Entity

Ive noticed that when using @s in Signs (Command Signs) and Command Blocks, It doesnt correctly Select the entity that is activating it, it just says "couldnt find entity" and only works when using a command in chat. I get this may be built into the game by default, Im not sure, but its extremely annoying, as Im running a realms with command blocks to activate and teleport the player that activates it, and players that are nearest to it get teleported, so with other players, I guess you can see how annoying it could get not being able to select and use the command on the one who clicks the sign/command block...

If this bug is Built into the game by default (works as intended) then why? Why is this feature not a thing... its very mentally painful to me that the command dialogue would show @s as a viable selector, and yet it doesnt work.