Earlier quoted context omitted.
I would say that you have to think in a different style so would classify as a different paradigm and not just syntax.
Going back to the original comment, the statement was that any experienced engineer could learn a language in a day. At risk of gatekeeping, I'd argue that by definition any experienced engineer would have some experience with an array based language like APL or MATLAB so that no, J does not qualify as a different paradigm.
So you can program in J like a C-programmer in a day. You definitely can't program like a J-programmer. And to say a competent engineer would already have array-language experience sidesteps the point.