The Big creature flag in some cases does not get respected and the boss get spawn regardless it being false.

I changed the "create_a_boss_here" function, and commented it out and add a print

if p then
    game.print("Blocking create_a_boss '" .. name .. "', config value is " .. tostring(storage.stg_allow_big_creature_cloud))
    return
    --local boss = surface.create_entity{name = name, position=p, force=force}
    --surface.create_entity {name="tb_poison_die_cloud_5",position=p, force=force}
    --storage.created_boss_tick = game.tick
    end

and it very rarely get called; it is very rarely like in multiple hours with max evolution.
I would post the print, but I didn't add the tostring(bool) so it crashed hahaha, but either way it shouldn't be called

actually, it can't be disabled, you disable it, the message pops up, it is enabled, like it doesn't save it some how....