When you place a command block, you're given the ability to execute commands based on redstone logic, this has worked in previous versions of Spigot. 1.13 changes the behaviour of selectors and removes/replaces many commands as well as the original selector attributes. 

Currently, selectors are not parsed when executing a plugin command via command block and are interpreted literally (e.g. /smite @p literally looks for a player named @p.) unless using a native command like /say. 

The attached image was produced by the input. 

/sudo @s bukkit:help

The user is a server operator.