I have never heard this theory, and I by all means am very Scandinavian. It sounds like something ... militaristic people would say, to be frank. Can you please describe more this theory and where you have heard it from?

Follow up question. Which of the three was the most powerful both militarily and economically?.

Ive never heard of this.

But I do know its broadly accepted that foreign(as in non-Northern European powers) would intervened everything one nation seemed to establish dominium maris baltici(Baltic Sea dominion). This was against the interest of many nations that relied heavily on trade, like the Netherlands, Great Britain and the Hansa. Examples of this includes:

• Lübeck helping the Swedes break away from the Kalmar Union
• The Hansa Leagues and Polish-Lithuanian Commonwealth refusal to allow the the Holy Roman Empire to build up a navy so they could invade the Danish Isles.
• Dutch, Brandenburg, Poland and Austria intervening in the Dano-Swedish War of 1658–60 so Sweden didnt completely conquer Denmark.