There is not one single other engineering profession I'm aware of that thinks a "portfolio" consisting of past employment is insufficient, or that has academic trivia questions figure as largely in their interview process.
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.
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.