onShippingChange make paypal guest checkout opening on separate windows

[daviddk8]

When clicking on paypal button an embedded form is opening on my page but if I uncomment the code with onShippingChange

},
// This is opening the Paypal guest checkout on separate window !!!
/*onShippingChange: (data, actions) => {
return basket.CalcShipping(data.orderID, data.shipping_address);
},*/
onError: (err) => {
changeInputEnable(restoreInputEnableState);
alert(err);
},

Embedded paypal is what I want as the picture below :

But with onshippingchange it open in a separate windows like the image below:

I can make it work with both solution but I didn't not find the explanation of this behavior in the documentation.