The VCS location of several Conan dependencies point to repositories which contain only recipes used to publish these packages on Conan Central, but not the actual source code of the packages.
As result the actual sources are not being scanned, see e.g. [1,2,3].

[1] https://bintray.com/conan/conan-center
[2] https://bincrafters.readthedocs.io/en/latest/
[3] https://github.com/bincrafters/conan-protobuf