-server is only a thing for HotSpot. They mention that HotSpot works perfectly fine. There is no option of "-server" for Graal native-image. It has "-O{0,1}" though for turning optimizations off and on respectively.
I think the project does have a bit of a naming problem. They've gotten the part out where it's very fast and pretty good, but everything is named GraalVM-something and it's not always entirely clear what's being referred to.