This is an auto-filed bug because sys-devel/cons installs compressed files (manpages, documentation). The issue was originally discovered on amd64, but it may be reproducible on other arches as well. If you think that a different summary clarifies the issue better, feel free to change it. Attached build log and emerge --info.
Created attachment 642304 [details] build.log build log and emerge --info
tinderbox has reproduced this issue with version 2.3.0 - Updating summary.