Plugin that implements onUserAfterSave not firing

-- HikaShop version -- : 5.1.5
-- Joomla version -- : 4.4.13
-- PHP version -- : 8.1.32

Hello,
I (vibe)coded a plugin to update my Mailchimp contacts with a new tag. My intention was that if they purchase on my site using Hikashop, they get tagged as a client.
The plugin implements the onUserAfterSave event and works if I save the user using the com_users component.
But the plugin won't fire after Hikashop creates a new user on my site, for instance during the order process.
My understanding is that Hikashop implements its own user API with onAfterUserCreate(&$element)
Does this mean I need to explicitly call this function in my plugin, if I want full integration with Hikashop?
Thanks in advance,
Brett