His claim was good although his reason was not perfect. The claim for SWE having a port by the sea in any scenario is
not only avoiding the trade tariffs, a more complete description of the reasons is
- this strip of land was used for export not merely to avoid the Sound due but probably more because it was a shorter road to the Sea from some parts of Sweden, for instance some parts of Bergslagen, with its iron, which was connected to this land strip via e.g. Klarälven and then lake Vänern and finally Göta Älv
- whether there were any naval
military base or not is not a prerequsite in this game for having a port (from where you got this notion is a mystery); do you for instance believe there was a naval military base in Baffin Bay just because EU has ports there, they were perhaps afraid of a military attack in that area well suited for military operations
- and last but not least: Sweden did own this piece of land with its port (at a place where some 200 years after the game starts Gothenburg was founded)
Thus the existence or non-existence of the Sound due in this game has nothing to do with the fact that Sweden did own this strip of land and that it had many effects on the nations involved some of which are excellently portrayed in the game and some else not.
Besides the Sound due
is partly implemented in this game by giving Sjaelland a very high tax value, only the reverse is not implemented, i.e. a reduction of trade income and an increase of price of import products for other nations.