The first two lines should output the same thing according to docs. The 3rd line is how characters currently behave. I have no explanation of what is going on on the fourth line, which would be the workaround for this inconsistency. If you try to run fourth line without the shape, it just hangs, so I do not know the contents of the resulting array, only its shape
△˙⊞⊟↯3_4 0 ## [3 3 2 4]
△˙⊞⊟↯3_4 @a ## [3 4 3 4 2]
△˙⊞₀⊟↯3_4 0 ## [3 4 3 4 2]
△˙⊞₁⊟↯3_4 @a ## [3 3 3 4 2]