It's essentially just a redirect ;)
Discussion
Nice.. I just wanted to confirm that this was the flow because it means there is only 1 transaction. Is not two (one from the sender to you and then from you to the receiver)
Correct. It's just one transaction.
I tested and is not working. I pasted a WoS LN Address and then I copy pasted nico@nostrplebs.com in the website lnurlpay.com to see if it recognizes it and is throwing and error
All this is doing is a redirect. Standard web technology. It's extremely simple. I just tested with a WoS address and it worked for me. Be sure that you're updating the field with the correct address from WoS.
Yes I am

You can see I added yellowaddress44@walletofsatoshi.com
But if you try to send 1 sat to nico@nostrplebs.com it doesnβt retrieve the invoice