authenticationPreemptive=true does not work with pollEnrich.
In Class /org/apache/camel/component/http4/HttpPollingConsumer.java:79 you see the following code:
The setup for authenticationPreemptive is missing.
You can see what to do in org.apache.camel.component.http4.HttpProducer#executeMethod:
In org.apache.camel.component.http4.HttpPollingConsumer#doReceive getEndpoint().isAuthenticationPreemptive() returns the correct value, so there is nothing against implementing this feature here as well.
The problem behind the scene ist that the context attribute "preemptive-auth" is missing.