Cloak of Arachnida- "Web" immunity not working

[Chandlore]

As title. I found this item, which I figured would be PERFECT for my Arcane Trickster... problem is, whenever I cast the spell, the immunity doesn't work. If this is intended, please ignore this post, but multiple people told me to post here. Whether using the Cloak's built-in daily Web, or casting it from my own spellbook, I'm still required to make a reflex save, and if I pass, I still get slowed. Does the immunity only apply to the Entangle effect? Is there any way to fix this, or should I just give up on the cloak?

[Tsidkenu]

Spell Immunity items only apply when spells are cast directly at the wearer, unfortunately. AoE and DoT spells (eg. Web, Cloudkill, Incendiary Cloud) are unaffected and continue to work as normal. If you wear a Spell Immunity: Silence item, for example, you will be protected from the direct target version but not the AoE ground-target type.