I posted a reply on your thread over yonder.
But, to summarize, I think they're using the word "open" to mean two different things in the sections on Magical Enchantments and on Talismans. In the Magical Enchantments, "open" seems to refer only to the initial preparing an item for enchantment, where you put the "material and size"-based amount of Vis into the item so it can hold future enchantments (which you don't need for lesser enchantments or charged items). In the Talisman section, it seems to use "open" to refer to any time you're fixin' to put another magical effect into the talisman. So, imo, I think that rule with Major Philosophic Alchemy refers to opening an item with regards to the Magical Enchantment and not to the Talisman rules.