Steps to reproduce

• Type /fill and it will come up with the syntax
• You will notice there will not be a ' {dataTag}

  ' at the end of the syntax

• BEFORE YOU CLOSE THIS AS WORKS AS INTENDED AND I SHOULD SUGGEST THIS IN MCSUGGESTIONS SUBREDDIT, please consider the fact that /fill is meant to work exactly the way /setblock does only being able to fill in a large amount of blocks in a cubic area, and /setblock does support dataTags