javadoc site creation ignores configuration parameters

how to reproduce:

% git clone https://github.com/hgschmie/pg-embedded.git
% cd pg-embedded
% ./mvnw clean install site

Point a browser at the local target/apidocs folder. The generated javadocs do not have a HELP menu item on top and references to Guava, JUnit5 etc. have been resolved and are linked.

Point a browser at target/site/apidocs. The javadocs here do have a HELP menu item and references to JUnit 5 etc. are fully qualified class names without links.

The debug log shows that the javadoc-no-fork goal is run with a lot of configuration options, including multiple duplicates:

[DEBUG] Configuring mojo 'org.apache.maven.plugins:maven-javadoc-plugin:3.3.1:test-javadoc-no-fork' with basic configurator -->
[DEBUG] (f) release = 11
[DEBUG] (f) source = 11
[DEBUG] (f) encoding = UTF-8
[DEBUG] (f) maxmemory = 1024m
[DEBUG] (f) quiet = true
[DEBUG] (f) doclint = none
[DEBUG] (f) show = protected
[DEBUG] (f) links = https://junit.org/junit5/docs/5.8.1/api/, https://javadoc.io/doc/com.google.guava/guava/30.1.1-jre/, https://javadoc.io/doc/com.github.spotbugs/spotbugs-annotations/4.4.2
[DEBUG] (f) author = false
[DEBUG] (f) detectJavaApiLink = true
[DEBUG] (f) linksource = true
[DEBUG] (f) nodeprecated = false
[DEBUG] (f) nohelp = true
[DEBUG] (f) skip = false
[DEBUG] (f) failOnError = true
[DEBUG] (f) release = 11
[DEBUG] (f) source = 11
[DEBUG] (f) encoding = UTF-8
[DEBUG] (f) maxmemory = 1024m
[DEBUG] (f) quiet = true
[DEBUG] (f) doclint = none
[DEBUG] (f) show = protected
[DEBUG] (f) links = https://junit.org/junit5/docs/5.8.1/api/, https://javadoc.io/doc/com.google.guava/guava/30.1.1-jre/, https://javadoc.io/doc/com.github.spotbugs/spotbugs-annotations/4.4.2
[DEBUG] (f) author = false
[DEBUG] (f) detectJavaApiLink = true
[DEBUG] (f) linksource = true
[DEBUG] (f) nodeprecated = false
[DEBUG] (f) nohelp = true
[DEBUG] (f) applyJavadocSecurityFix = true
[DEBUG] (f) author = true
[DEBUG] (f) bootclasspathArtifacts = []
[DEBUG] (f) bottom = Copyright © {inceptionYear}–{currentYear} {organizationName}. All rights reserved.
[DEBUG] (f) breakiterator = false
[DEBUG] (f) debug = false
[DEBUG] (s) destDir = testapidocs
[DEBUG] (f) detectJavaApiLink = true
[DEBUG] (f) detectLinks = false
[DEBUG] (f) detectOfflineLinks = true
[DEBUG] (f) docencoding = UTF-8
[DEBUG] (f) docfilessubdirs = false
[DEBUG] (f) docletArtifact = groupId = 'null' artifactId = 'null' version = 'null' classifier = 'null'
[DEBUG] (f) docletArtifacts = []
[DEBUG] (f) doctitle = pg-embedded 4.1-SNAPSHOT API
[DEBUG] (f) encoding = UTF-8
[DEBUG] (f) failOnError = true
[DEBUG] (f) failOnWarnings = false
[DEBUG] (f) includeDependencySources = false
[DEBUG] (f) includeTransitiveDependencySources = false
[DEBUG] (f) isOffline = false
[DEBUG] (f) javaApiLinks = {}
[DEBUG] (f) javadocDirectory = /Users/henning/code/pg-embedded/src/main/javadoc
[DEBUG] (f) javadocOptionsDir = /Users/henning/code/pg-embedded/target/javadoc-bundle-options
[DEBUG] (f) keywords = false
[DEBUG] (f) links = []
[DEBUG] (f) linksource = false
[DEBUG] (f) localRepository = id: local url: file:///Users/henning/.m2/repository/ layout: default snapshots: [enabled => true, update => always] releases: [enabled => true, update => always] blocked: false
[DEBUG] (f) mojo = org.apache.maven.plugins:maven-javadoc-plugin:3.3.1:test-javadoc-no-fork {execution: null}
[DEBUG] (f) nocomment = false
[DEBUG] (f) nodeprecated = false
[DEBUG] (f) nodeprecatedlist = false

[DEBUG] (f) nohelp = false
[DEBUG] (f) noindex = false
[DEBUG] (f) nonavbar = false
[DEBUG] (f) nooverview = false
[DEBUG] (f) nosince = false
[DEBUG] (f) notimestamp = false
[DEBUG] (f) notree = false
[DEBUG] (f) offlineLinks = []
[DEBUG] (f) old = false
[DEBUG] (f) outputDirectory = /Users/henning/code/pg-embedded/target/apidocs
[DEBUG] (f) overview = /Users/henning/code/pg-embedded/src/main/javadoc/overview.html
[DEBUG] (f) project = MavenProject: de.softwareforge.testing:pg-embedded:4.1-SNAPSHOT @ /Users/henning/code/pg-embedded/pom.xml
[DEBUG] (f) quiet = false
[DEBUG] (f) reactorProjects = [MavenProject: de.softwareforge.testing:pg-embedded:4.1-SNAPSHOT @ /Users/henning/code/pg-embedded/pom.xml]
[DEBUG] (s) reportOutputDirectory = /Users/henning/code/pg-embedded/target/site/testapidocs
[DEBUG] (f) resourcesArtifacts = []
[DEBUG] (f) serialwarn = false
[DEBUG] (f) session = org.apache.maven.execution.MavenSession@119c745c
[DEBUG] (f) settings = org.apache.maven.execution.SettingsAdapter@70331432
[DEBUG] (f) show = protected
[DEBUG] (f) skip = false
[DEBUG] (f) sourceDependencyCacheDir = /Users/henning/code/pg-embedded/target/distro-javadoc-sources
[DEBUG] (f) splitindex = false
[DEBUG] (f) staleDataPath = /Users/henning/code/pg-embedded/target/maven-javadoc-plugin-stale-data.txt
[DEBUG] (f) stylesheet = java
[DEBUG] (f) tagletArtifact = groupId = 'null'

Especially the "nohelp = false" is concerning because that has been set to "true" everywhere in the pom.