I can confirm this is an issue on MacOS 11 Beta 8 (as well).
Bottom Line: The delegate java commands use JAVAVERSION to route to the correct JDK, not JAVAHOME. So, Set JAVA_VERSION="1.8".
Set JAVA_HOME too, but that's for other tools.
The binaries /usr/bin/java and /usr/bin/javac (etc) are all the same binary which (I'm guessing) launch the correct command based on examining its first parameter and (as of Big Sur) the JAVA_VERSION environment variable.
You can set JAVA_LAUNCHER_VERBOSE=1 to get output its assumptions about paths and versions.
Helper
For anyone reading this who is NOT a super expert on all this JDK stuff, you can add helpers to your shell init: some variation on:
switch_java() {
		export JAVA_HOME=$(/usr/libexec/java_home -v $1)
		export JAVA_VERSION="$1"
		echo "JAVA_HOME: ${JAVA_HOME}"
		echo "JAVA_VERSION: ${JAVA_VERSION}". ####	WORKAROUND 		java -version
}
java8() { switch_java 1.8 }
java11() { switch_java 11 }
NOTE: Setting JAVA_VERSION as well as JAVA_HOME.
$ java8
JAVA_HOME: /Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home
JAVA_VERSION: 1.8
openjdk version "1.8.0_265"
OpenJDK Runtime Environment (Zulu 8.48.0.53-CA-macosx) (build 1.8.0_265-b11)
OpenJDK 64-Bit Server VM (Zulu 8.48.0.53-CA-macosx) (build 25.265-b11, mixed mode)
$ java11
JAVA_HOME: /Library/Java/JavaVirtualMachines/zulu-11.jdk/Contents/Home
JAVA_VERSION: 11
openjdk version "11.0.6" 2020-01-14 LTS
OpenJDK Runtime Environment Zulu11.37+17-CA (build 11.0.6+10-LTS)
OpenJDK 64-Bit Server VM Zulu11.37+17-CA (build 11.0.6+10-LTS, mixed mode)
and so on.
Topic:
App & System Services
SubTopic:
Core OS
Tags: