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.
Duplicates MC-121827