Once the Soul Lessons of one Twin Flame are learned, the other benefits from the overall Soul Growth since both Twin Flames share a Soul.
You as a Twin Flame partner will also realize that your Soul Lessons have not been for you alone because of the shared Twin Flame energy. You are constantly feeling your Twin Flame in yourself.
Separation is very important for Soul Growth because you need to grow strong in yourself on your own to be able to merge harmoniously both in your Twin Flame energy and the physical world.
Sometimes separation is needed for both Twin Flames to first fix their life situations because Twin Flames find each other in the rarest life circumstances; one may be married, or may have children, or could be going through a tough life situation and sometimes one Twin Flame could be battling with a Fatal disease when they meet.
Your life does not magically change and align with your Twin Flame; this is what most Twin Flames Learn after constantly chasing your Twin Flame.
Each Twin Flame lives a physical life that they previously thought was normal until they meet their divine partner.
Separation can be mutual, forced or uncontrolled.
When it is mutual, you both decide to give each other space. When it is forced, one Twin Flame can just disappear with no particular reason which is called running, and the most heartbreaking kind of Separation is the uncontrollable one.
In uncontrollable situations, Twin Flames can be separated due to geographical locations, language barriers, cultural differences or death.
I hope this helps.