[MC-121827] Selectors and scoreboards not working for signs (works correctly for books, /tellraw, and /title)

When typing in commands such as:

/title @a title [{"selector":"@p"},{"score":{"name":"@p","objective":"obj"}}]

/tellraw @a [{"selector":"@p"},{"score":{"name":"@p","objective":"obj"}}]

/give @a minecraft:written_book{title:"",author:"",pages:["[{\"selector\":\"@p\"},{\"score\":{\"name\":\"@p\",\"objective\":\"obj\"}}]"]}

/give @a minecraft:sign{BlockEntityTag:{Text1:"[\"name: \",{\"selector\":\"@p\"}]",Text2:"[\"score: \",{\"score\":{\"name\":\"@p\",\"objective\":\"obj\"}}]"}}

/title, /tellraw, and the book works fine, but the sign shows the raw selector and no score.