PayPal guest checkout is still listed as an available payment option here: FAQ: What payment methods are supported on Swappa? - Swappa
I shared my experience with PayPal and Swappa in a different thread:
Based on my experiences of shopping on Swappa, it’s up to the seller to enable this option.
For one of my recent purchases, one listing showed something similar to what is depicted in the image you shared; another listing showed a toggle between guest check out (does not show any links to privacy policy or TOS) and creating an account (does show those links).