Yes they spawn more,
other day 1 medium SOTD spawned right front of me, ill stop, SOTD dont move, i turn right SOTD turns right. i outsail that medium SOTD and another spawns left of me i go straight line ahead again third medium SOTD spawns, this goes on 6 medium SOTD until 7th medium SOTD spawns right front of me, and it was red. Then i decide turn left and go between 2 of medium SOTD, was able to outsail them.
Ill quess that sloop you could not have able to outsail medium SOTD.
Maby next patch we start seeing tiny SOTD.
