Trying to execute:

/scoreboard objectives add test dummy Test
/scoreboard players add @p test 1
/tellraw @p {"score":{"name":"@p","objective":"test"}}

will result in:
No such argument "target" exists on this command.

Trying the equivalent as a title command will not show the score component.
It does show it as a valid command and runs it.

It seems the "score" text component is broken.