/Title Subtile can't show the text but show "Showing new subtitle for <player_name>

Subtitle Command Problem

What I expected to happen was...:
When i use /title subtitle comand is will work 
Sample: /title @p subtitle {"text":"hello"}
=> the subtitle on chat will be: hello

What actually happened was...:
and what is happened when i use exactly command from Sample
but it's become "Showing new subtitle for <player-name>"

Steps to Reproduce:
1. use command /title subtitle
2. export subtitle chat "Showing new subtitle for <player_name>