Checkout UI Extension useCustomer doesn't update on "known customer"

[cloder]

Context

I'm working on a Checkout Extension UI app, and I need to get customer information when the purchaser enters their email.

The issue

According to the Buyer Identity docs, the `useCustomer` hook:

Returns the current `Customer`. The value is `undefined` if the buyer isn't a known customer for this shop or if they haven't logged in yet.

If I enter the email of a returning customer, the phrase "known customer for this shop" seems to indicate that the customer would be returned, even if they aren't logged in. 

It does not work.

Is there a way to retrieve customer data based solely on the email? Specifically, I need to retrieve a customer's metafields

[Strydar]

Hi, any workaround for this? I'm not able to make the useCustomer() api work as well.