If a person who doesn't play piano told me they have a piano solo in their head, i would set them up with a midi sequencer so they can bring it to life. My preconceptions about their capabilities are irrelevant.
A MIDI sequencer is not a piano, and mathematicians typically don't use maple/mathematica/octave/python (unless they're in applied maths, which is a subset of mathematics as a whole).
The most important breakthroughs in mathematics, the kinds of things that push you over the edge as a society and that expand the scope of humanity's knowledge, are at the proof level, which those programs cannot achieve.
Your MIDI sequencer analogy is very apt, because while someone may be able to bang something out on the MIDI sequencer and have the computer play it, a MIDI sequencing is not a human piano performance.
But you're right, if you want a hollow fascimile of the real thing, then yes, those tools could work to impress someone.
I’m no mathematician, but I’d be very surprised if the overlap these tools have with mathematical research is very large.