Entity scores do not display in tellraw/any JSON formatting

when using players(either with selector or name) scores to display in tellraw the scores display fine
if one instead tries to use an entity using a selector, the score will not display

Steps to reproduce:

Create a flat world, preferably redstoneready so that no animals can spawn
Spawn a Pig
/scoreboard objectives add temp dummy
/scoreboard players set @e[type=Pig] temp 5
/scoreboard players set @p temp 5
/tellraw @a {score:{name:'@p',objective:'temp'}}
/tellraw @a {score:{name:'@e[type=Pig,c=1]',objective:'temp'}}

The first tellraw outputs the number 5
The second tellraw outputs an empty line