How does the unusual rule for dissolving Swedish Parliament come about?

Sweden - unlike other European countries - has a Parliament that serves fixed 4-year term.

The Government can order extra elections to take place in between the 4-year term, but the extra elections do not change the fixed timetable of regular elections.

For instance, if an extra election takes place 2 years into the 4-year term, the election that comes after will be scheduled to take place 2 years later as planned.

I'm curious what caused this arrangement during Sweden's constitution drafting process? Is this a compromise between different parties? What is the central disagreement that led to this compromise?