If the argument made by the article linked to in the OP here (full disclosure: I’m the OP! But not the article’s author) is correct, then a virus which is wholly novel to almost all of humanity will disproportionately target the old since their immune systems don’t do the generic response as well as the young, and they don’t have any specific responses (antibodies, memory cells, etc) for a novel pathogen. If you wanted to target the young, you’d pick something that’s highly virulent but not novel, like measles (but without the vaccine availability.)
And if the argument in that article is not correct, I’d love to understand why!
(note: SARS-CoV-2 meets the test for novelty for the vast majority of humanity. The number of people who have been exposed to similar viruses - SARS and MERS - is very small, though survivors of those diseases would likely have had a better go against SARS-CoV-2.)