The article paints a sad picture ...although your conclusion seems far fetched. Even marriage can be made into paid rape by the wordings of that article.
AFAIK ... decriminalization allows for
1. The sex worker to approach authorities without any fear of prosecution.
2. To set up freelance sex work without pimps and brothels.
There shouldn't be a debate about this. Criminalization makes things worse at the expense of moral tidiness.
Regulated sex work allows for
1. Brothels
2. Strip clubs
3. Massage parlors
4. Sex Therapists
If the regulators are corrupt or weak or there are no strong checks ... then the model will be as bad as an unregulated market and will actually be worse as it allows trafficked victims to work under quasi-legal protection. That's what the article implies.
From what I know the nordic model has a large number of social services that help sex-workers quit the profession if they wish to and helps sex-workers unionise.
My views are largely shaped by the sex worker in
https://www.youtube.com/watch?v=1DZfUzxZ2VU
Criminalizing doesn't even offer protection for the sex worker. I'd rather argue about that than having some debate on numbers.