Nope, Build. should fit your lifestyle. If you are committed to a certain class one day and want to swap out the session in Build. for that, go ahead. Or, If you’re just looking for some new workout ideas and want to mix Build. into your usual workouts then 100% go for it!
Saying that, I definitely don’t recommend adding extra sessions if you’re following the programme if you want the results to work because it’s all been thought out in a way where the rest days and moves allow you to recover optimally before hitting them hard again. The sessions are intense, and the week is about having 5 highly intense sessions - recovery is when the muscle growth happens, so we need to prioritise and really protect it.