Apparently the information text found under a user’s profile link setup for YouTube is inaccurate (see first screenshot below). When someone adds only their channel “url” or “custom url name”, it unexpectedly directs to the BlenderArtists domain and not the expected YouTube domain.
Example: YouTube profile link
Result: When hovering over YouTube link (see lower-left corner)
One another besides me, and also Fweeb, who graciously suggested me to include him in this PM, have been able to confirmed this bug as well.