Sweden has stayed consistent with what experts have been saying. There's no use in closing the borders when the virus is already in the country.

Same thing with outlawing movement in and out of Stockholm. There's already a very clear recommendation and instruction to avoid travel within the country to avoid spreading the virus. There's no real way of enforcing a full quarantine unless you divert police officers who could be doing other things, or the military which we are reluctant to do (see Ådalen 1931, which is a reason why you don't want armed military to interact with citizens).