Change in Twin Flames is Alchemical. There is no degree to which you can measure it or influence it. The Soul Cleanse process will transform the two individuals who are involved in the Twin Flame Journey until they are both transformed into their Authentic beings.
If you look at it from the energetic point of view, both Twin Flames share the same core signature vibration. This means that there is no distinction between the two energies of the divine partners; (chaser or runner).
As the Twin Flames grow into their Twin Flame energy by learning to balance it within themselves, the two individuals strengthen their core shared Twin Flame energy.
When you quiet yourself from within and listen to your soul, you will feel your Twin Flame feel you back. You just know in your gut how they are feeling for you by feeling the energy within yourself because your Twin Flame is you.
Yes, physical change can happen and sometimes it seems drastic but I challenge you to look at this from an energetic perspective not from a physical separation point view because Twin Flames are each other.
The right answer can only manifest once these two individuals physically meet again, here you can be able to tell the physical growth that has happened for each Twin Flame.