I think the idea there is that, ECM being the only e-war type available to Caldari ships, and ECM being powerful enough to make any ECM ship the primary at the outset, the Caldari would develop a hyperdurable ECM platform.
The Widow builds on this by actually adding some DPS bonuses alongside the e-war.
But…who knows really. Yet another example of the bizarre concept of “racial flavor” that CCP falls back on when criticized about this and the kinetic damage bonuses on many Caldari ships.