This behavior has been present since at least CL 4433047, 9 years ago.
We presumably cannot change it at this point, since un-ignoring these files could break existing packages. We would need to gate the change on the go version specified in the go.mod file, and that degree of complexity does not seem worthwhile to me just to open up one package name — but if you feel otherwise, please feel free to open a separate proposal.
I think the most we can do without an invasive breaking change is to document the current behavior.
changed the title
cmd/go: go list fails on package containing single file with magic "documentation" package nameApr 27, 2020