JSON - Entity data problem with selector input

I noticed a problem with JSON "selector" input when merging entity data, more specifically the entity's name. (Minecraft 1.13-pre9 version)

At first, I managed to write a player's name on a sign (Block data.png image):

/data merge block <x> <y> <z> {Text1:"{\"selector\":\"@p\",\"color\":\"blue\"}"}

Then, I tried the exact same thing for an entity's name (Entity data.png image):

/data merge entity <entity> {CustomName:"{\"selector\":\"@p\",\"color\":\"blue\"}",CustomNameVisible:1}

Instead of writing the player's name, it just wrote "@p", which is not normal.