I've been tracking the levels of recipes I receive as the reward for turning in a crafting provisioning writ. My lower skill toons get recipes at two levels, at and right below, their skill level. e.g.
My level 13 / provisioning skill level 4 toon gets both 40 and 45 level recipes.
The CP160 / provisioning skill level 5 toon gets both cp10 and cp50 level recipes.
My CP160 / provisioning skill level 6 toon has only been getting cp150 level recipes. No cp100 level recipes.
Environment looting and theft does get some cp100 level recipes with the lvl 6 toon.
So it appears to be a bug that level 6 provisioning skill doesn't get level cp100 recipes as a writ reward.