First noticed this behavior in 12.3-rc-1 that upgraded solr from 8.1.1 to 8.5.1 - see discussion:
The Tomcat service does eventually stop after 60+ seconds. In XWiki 12.2.1 the issue is not present and the Tomcat service stops very quickly and does not hang.
There appears to be a searcherExecutor thread that hangs when stopping. Creating issue here per Thomas Mortagne for tracking.