My sister came back home from UK to Croatia for a couple of years but didn't want to teach her kid Croatian insisting he should speak English (as they eventually went back to UK).

This was a terrible choice - he couldn't socialise with local children (preschool age) and is severely underdeveloped in that area, plus his vocabulary isn't that developed as the only place he heard English was at home.

Maybe the Swedish policy works for school age children, but preschool - I very much doubt it without special education programs.