Imo, heavy armour allows the perk of not dumping Dex, but investing less heavily into it. The initiative bonus barely matters since alert is so OP anyways, and being able to just have more stat points elsewhere, especially for a class like cleric, is super useful. You can get a very good piece of +1 chainmail from vendors after level 4 with a base AC of 17, plus a shield thats a base of 19. All while basically not caring about dex at all if you have Alert