The contactless reader is compatible with that device. https://squareup.com/shop/hardware/us/en/products/chip-credit-card-reader-with-nfc
I don't have the pixel 4 XL. But I do have the pixel 4A and the only way to get my reader to work with my phone is I had to have the adapter at the bottom of the phone in order to hook in the square.
I hope this was helpful.