Auras and resource trickle can severely unbalance a game, therefore it's perfectly understandable such entities are limited. War dogs have an entity limit because they move around and require 0 population.
However, fortresses and towers currently have entity limits too; this patch removes those. Defensive structures don't have auras, don't give a resource trickle, and don't move around. Moreover, their minimum distances prevent them from being massed and in practice their costs limit their numbers too. Civic centres and military colonies don't have entity limits either (except in the village phase). These entity limits for fortresses and towers unnecessarily restrict player freedom, especially on giant-size maps. See also comments by various people on the forums (e.g. https://wildfiregames.com/forum/topic/37687-lets-fight-gameplay-balance-mod/page/2/?tab=comments#comment-422251 ).
Furthermore, the minimum distance between fortresses is raised from 80 to 90 to compensate (also for the different way attack ranges are calculated: #3381 / D2759 / rP24127).