You are overthinking it.
Finished box depends on downloaded box.
There are pretty obvious icons indicating things (downloaded symbol. and finish line symbol).
I thought it was pretty intuitive and never required an explanation.
Now that you know, try using it for a bit
And it is fairly common to have a 3 state box. MS windows does it all the time to indicate "partial".
for example if you compress one file. then check the entire folder. you will see partial box state for compression.
same for read only and hidden.
here are 3 different box states for read only in windows
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