I dunno, I think regression tests are inherently boolean. Either it passed or it didn't. The code path that the system takes to get to a green light or not is arbitrary. If you start using an enum to return the result of the test, folk tend to add more and more enums over time until it's overly complicated. Processes return an 8 bit integer, but 99% of the time all anyone checks is whether it was 0.
There's certainly practical benefit to being able to quickly triage a test failure. Tests that only output booleans are annoying. When there is a failure, it's helpful to have some out-of-band information about why it failed. That's typically provided via console output, but you can make whatever complex logging system you want.
If a regression test fails, you alert the programmer who kicked it off and maybe roll back the checkin.
If the regression testing system has an error while running a test, you page the oncall SRE and maybe try to rerun it. You certainly don’t roll back any checkins.
There's certainly practical benefit to being able to quickly triage a test failure. Tests that only output booleans are annoying. When there is a failure, it's helpful to have some out-of-band information about why it failed. That's typically provided via console output, but you can make whatever complex logging system you want.