This seems to have been partially resolved as part of the changes to MC-165562
However, the resolution to MC-165562 seems to not be fully complete.
To demonstrate this, typing /tp and backing out of the TAB suggestions now correctly displays the argument suggestions. However, typing /tp William278 and pressing space will display the error, despite there being valid additional arguments a user could pass to the command. In that case, typing a single character will then display the argument suggestions list.
At the very least, the "inconsistent between commands" part of this issue has been fixed as of Pre-2, as this behaviour is consistent between /tp and /teleport; it was not before. It remains inconsistent between arguments.
This seems to have been partially resolved as part of the changes to MC-165562
However, the resolution to MC-165562 seems to not be fully complete.
To demonstrate this, typing /tp and backing out of the TAB suggestions now correctly displays the argument suggestions. However, typing /tp William278 and pressing space will display the error, despite there being valid additional arguments a user could pass to the command. In that case, typing a single character will then display the argument suggestions list.
At the very least, the "inconsistent between commands" part of this issue has been fixed as of Pre-2, as this behaviour is consistent between /tp and /teleport; it was not before. It remains inconsistent between arguments.