Certainly achievable. Usually by the time you finish the course.
The trick is to get three things working. Don’t miss a note. Alternating plucking. Getting it up to speed for the fast workout.
It’s doable, but it is one of the harder songs in the whole course. The reason it gets so much attention is when it appears in the course. It’s a huge jump up in difficulty compared to what you will have learned up to that point and I think that takes a lot of people by surprise.
And, Billie Jean is such a deceptive little sh!t. It doesn’t seem hard… at first.
Then the finger twisting bites you in knuckles.