Some users end up generating BTs routinely during their ZRL events on Zwift or on hard group rides outdoors or a tough hill effort like @Garrick describes.
Once your signature is dialed in it will track closely based on changes in TL alone. BTs are not absolutely necessary but chasing down a BT on occasion will validate where you’re at.
Here is a post where I describe the different fitness tests in the Library –
From old trainer to smart trainer. Set FTP - Training - Xert Community Forum
These workouts won’t show up on recommended workout lists but you can pick one any day you’re feeling fresh and rested and want to validate your signature. Even if you don’t generate a BT or Near BT you’ll know how close you were by the MPA graph on the activity chart.