What is "Radan HTTP"?
The port itself (8088) was originally registered to Radan for vendor-specific HTTP traffic. It has since been co-opted by the general public for use for proxies (along with 8000, 8080, 8888).
I have a feeling it's not Nginx identifying itself as Radan, but that the software you are using to scan is just referencing the IANA port list.