When a tadpole grows up into a frog, the subtitles display "subtitle.entity.tadpole.grow_up" instead of something better formatted

What I expected to happen was...:

The subtitle should read something like "Tadpole grows up" when a tadpole grows into a frog

What actually happened was...:

The text outputted is "subtitle.entity.tadpole.grow_up"

Steps to Reproduce:
1. Turn on subtitles
2. Hatch a tadpole, and wait for it to grow up