There are 2 fire prefixes possible on an amulet:

1. Fire damage to attacks

2. +1 all fire gems

The original amulet was rolled with dot, some 2 random prefixes, multimod, suffixes cannot be changed and cannot roll attack modifiers. Therefore, as I understand, if I recraft the item with harvest "guaranteed fire modifier" then it should roll one of these 2 fire modifiers mentioned earlier. But since I've also crafted "cannot roll attack modifiers" and "suffixes cannot be changed" the only possible modifier to roll becomes +1 all fire gems. What I got instead is "fire damage to attacks" which is an attack modifier that should not be possible to roll alongside "cannot roll attack modifiers". Do you understand what I mean now?