Definitely makes you question it more. Does the paper not explain the contents of the MATLAB code? That's all that is usually needed for reproducibility. You should be able to get the same results no matter who writes the code to do what is explained in their methods.

Of course, I have no idea about the paper you're talking about and just want to say that reproducibility isn't dependent on releasing code. There could even be a case were it's better if someone reproduces a result without having been biased by someone else's code.