This example uses the old API based on the use of "Create", so you used:
client.Create person
Now you can (and should) use the Cypher version:
let createPerson person =
client.Cypher
.Create("(p:Person {param})")
.WithParam("param", person)
.Return<Person>("p")
.Results
.Single();
let pA = createPerson { Name = "PersonA"; Twitter = "tA" }
. Cypher - db.