We don't define Christian music by just the lyrical content but we may also include artists who have made public stance for Christ.
We may not necessarily feature or promote music from those artists, but if they belong to the body of Christ, we want to provide access to those who may wish to listen to them
eg If we define Christian music by the lyrical content, what do we do with an instrumental artist who is a Christian.
What about a mainstream pop artist who is publicly Christian (personal growing relationship with Christ) and who doesn't have music that compromises biblical worldview but whose songs are not necessarily about Christian topics? Tori Kelly, Brook Fraser - both who are known in the pop/mainstream realms while also being worship leaders in their local churches.
On the flipside, what about Christian songs sung by artists who are not Christians - there are many hymns sung out there by artists who have not made a public stance as a Christian, and whose other content contradicts the biblical worldview. We don't include these songs or artists, as many may say "Lord, Lord..."
Christmas is the exception we typically make. eg O Holy Night was written by two unbelievers who were not living by biblical standards... and there are other artists who make great contributions to the Christmas canon of music, who may not be Christian or have other Christian music. We carefully include these case by case. We recognise that not everyone will receive them the same way, but we choose to do this unless their Christmas content can be shown to be problematic.
We do get complaints about heavy metal bands who are publicly Christian in content and character, but because they don't sound Christian, some users may not appreciate that... we do not take personal music or subjective theological viewpoints into account. We don't have it perfect, and we are willing to review any band or song that you feel is inappropriate.