For you outside Sweden: There is no such thing as minimum wage. It's perfectly legal to hire someone for 0 SEK / month.
The whole idea is that a collective agreement should be negotiated and agreed upon by the employers and employees in each business area (like telecom, healthcare, factory workers, electricians etc etc). The idea is that the employers and employees, not the politicians, knows more about what their market/business area requires and is able to deliver in the form of minimum wage, yearly salary increase, vacation and overtime (among other things) .
Here's the thing that often is different in discusions like the one about Tesla refusing to sign a collective agreement: Collective agreements only limits the minimums. So the only reason to refuse to sign is if you intend to keep some thing below the levels that are the norm in your business area.
Essentially, you're trying to get unfair competitive advantage.