What I meant by "broadening experience" is not a hobby-level stuff you describe (still very useful on a personal development level) but gaining enough depth in another field to be comparable to an undergraduate with that specialization; or at least with a minor in that area. It is a higher bar, but someone with good CS background can master the equivalent of the 3-5 higher undergrad level classes pretty quickly.
I agree that software companies are not really interested in non-software hobby projects. But non-software tech companies often put a very high value on software as a secondary skill in their non-software hires and are willing to lower the bar for their primary tech competency. My 2c.