To me a request for portfolio contents beyond the contents of a resume is an indicator that the would-be employer is interested in people who are easily exploited or cajoled into working lots of unpaid overtime, or else that they don't actually trust the candidate's resume; both of these are negative indicators. A heavy focus on DS/algorithms for engineering positions is an indicator that the employer either doesn't understand the difference between academics/theory and engineering or, worse, thinks the latter is trivial, irrelevant, or otherwise beneath CS; both also negative indicators.

I do like programming, and I can at least empathize with the parent's skepticism. I do recall the lessons that my other freelance colleagues have told me about 'work-for-free' schemes in different forms. I don't think that's what is happening here but I can understand why some might feel that way.