Well, it's just me.Not that I am aware of, I'm happy to run some vanilla tests if you have situations.
I had not realized that the global parameter "COMBAT_HEAL_CITY_GARRISON" (default value = 20) controls both the healing of units garrisoned in cities and the city itself, I was assuming it was only for the city... Well, now I just need to get ride of that parameter and use my own functions for city healing.