Connecting customer account to checkout via store

[yklym1]

Hello everybody! 

I am a little bit confused about the way storefront API works regardless "CheckoutCustomerAssociate" mutation. 

I use it like this 

mutation CheckoutCustomerAssociate(
    $checkoutId: ID!
    $customerAccessToken: String!
  ) {
    checkoutCustomerAssociateV2(
      checkoutId: $checkoutId
      customerAccessToken: $customerAccessToken
    ) {
      checkout {
        webUrl
      }
      checkoutUserErrors {
        code
        field
        message
      }
    }
  }

but the result I get can differ due to the user's device. For example, some guys from our team get it like this: 

while most of the users just get email field prefilled 

Personally, I can't get the first scenario even when I try the same account as the screenshot's author did. I'm wondering, what can cause such differences in the behavior and how could I achieve them both.