The bug
The syntax help for the /clone
command is missing the case where filtered
is chosen as maskMode. In this case the cloneMode and an additional block argument are required.
How to reproduce
Use the following command
/clone ~ ~ ~ ~ ~ ~ ~ ~1 ~ filtered
→ It will show you the syntax help despite the fact that the used command matches the printed required syntax
Suggested syntax help
/clone <x1> <y1> <z1> <x2> <y2> <z2> <x> <y> <z> [replace|masked [<cloneMode>]]|[filtered <cloneMode> <block> [<dataValue>|<state>]]
or
/clone <x1> <y1> <z1> <x2> <y2> <z2> <x> <y> <z> [<maskMode>] [<cloneMode>] OR
/clone <x1> <y1> <z1> <x2> <y2> <z2> <x> <y> <z> [filtered <cloneMode> <block> [<dataValue>|<state>]]
Fixed in some 1.13 snapshot.