Simple example if you use wildcard exclusions your build will fail because it's available only with maven 3.3.3 and the current embedder will reject the pom as a failure whereas it's not.
This plugin has some technical constraints (defaults..) so it's impossible to manage such legacy builds and upgrade for new features and/or security reasons.
BTW we are now in 2019j jdk6 and jdk7 are definitely EOL/DEAD
one day we have to stop trying to maintain those very old/legacy...
If it's a big issue for you you can definitely use freestyle or pipeline plugins, use maven toolchain, configure compiler target/source attributes, animal-sniffer plugin.... few options.