Hi Francisco,
It could be that given SceSim is not a SpringBoot-based test (doesn't need to start the spring-boot-web infra etc) then the SB configuration are not picked up as indeed that is something pertaining to Spring Boot.
On other hand, Drools, Kogito, etc. rely on vanilla SLF4J.
Given org.springframework.boot:spring-boot-starter brings Logback as the default logging implementation in the classpath (instead of say Log4j or any other logging backend), Logback does not find its vanilla configuration files (those logback.xml).
Hence, in order to properly configure Logback when non-SB unit tests are running, the standard Logback configuration is needed.
That is the most realistic explanation I could think of so far.
Hope this clarifies, thanks also Gabriele for contributing to this conversation!
MM