Hi Mor, thanks. Yes, this case is also frequent (!)… The proposal,
GitHub - ppKrauss/licenses: proposal for CSV of licenses, see https://github.com/datasets/registry/issues/118
is also about implied licenses, as you describe, with no explicit citation of licence in the document…
And the worse, yes perhaps is not so rare 
In order to overcome contradictions, we need some RFC-like process to endorse “implied licenses reports” …
The brasilian report is a good example,
licenses/implied-lex-BR-v1.md at master · ppKrauss/licenses · GitHub
There are also other drafts to show that is not difficult,
licenses/implied-lex-IL-v1.md at master · ppKrauss/licenses · GitHub
licenses/implied-lex-IS-v1.md at master · ppKrauss/licenses · GitHub
licenses/implied-lex-US-v1.md at master · ppKrauss/licenses · GitHub
…
and, of course, the worst case is when we must use the “universal default”,
licenses/implied-berne-v1971.md at master · ppKrauss/licenses · GitHub
