Consider:
Are you expecting the result to be [3, 2, 1, (0-1-2-3)] --> [3, 2, 1, -6] a vector of 4 elements? Or are you expecting [3, 2, 1, 0, -1, -2, -3] a vector of 7 elements?
Inside [] and {}, if you have VALUE1 -VALUE2 then that is treated as [VALUE1, uminus(VALUE2)] where uminus is unary minus. Likewise inside [] and {}, if you have VALUE1 +VALUE2 then it is treated as [VALUE1, uplus(VALUE2)] where uplus, + is unary plus. If you have VALUE1-VALUE2 or VALUE1- VALUE2 or VALUE1 - VALUE2 then those are all treated as minus(VALUE1, VALUE2) but VALUE1 -VALUE2 is unary operator not subtraction.
I suspect that your expectation is that inside [] and {} that VALUE1 -CONSTANT is treated as [VALUE1, negative_CONSTANT] and that your expectation is that VALUE1 -non_constant_EXPRESSION is treated as minus(VALUE1, non_constant_EXPRESSION) but as far as the MATLAB parser is concerned, [VALUE1 -CONSTANT] and [VALUE1 -non_constant_expression] have the same form.
