This isn’t an argument against credentialling since it is literally the direct effect of not having credentialling in software. Credentialing cuts most-to-all of what would be the low tail of the profession off before it ever enters. Nurses and lawyers who can’t do their profession’s equivalent of fizzbuzz mostly wash out of the exams to enter the profession (or earlier), they don’t show up in job interviews, except where the inability is produced by some kind of post-entry decline in capacity. And even then, decertification is a real possibility, which further purges the low end of the distribution.
So, yeah, a -1σ software developer (or at least software developer job applicant) is worse compared to basic expectations than a -1σ nurse, because a nurse as below expectations as a -1σ software developer is would be compelled to find a different profession because of credentialling requirements.