It seems that as of late, Scap no longer sets the level attribute in its Logstash messages.
https://logstash.wikimedia.org/app/kibana#/dashboard/mwdebug1002
Instead, it seems to set an attribute called loglevel which isn't what MediaWiki, syslog and all other production services use for the severity. I couldn't find anything obvious in Puppet that changed so I suspect it might be due to a change in Scap itself.