execute if/unless block outputs the wrong error message when querying unloaded blocks

How to recreate:

Attempt to use the command:

execute if block 99999 1 1 cake run say wow

making sure of course that those coordinates are unloaded.

You will get the output 

"Unknown or incomplete command", despite the fact that the command is both known and complete.

Note that you must have a run command. Just querying the block directly, like: 

execute if block 99999 1 1 cake

will work properly.

I am not able to recreate this in 1.19.4, so I believe this is a new issue.