It is not out of spite but rather out of fear and insecurity — The runner regrets their actions after they learn about the nature of the Twin Flame experiences.
From the chaser’s perspective, the actions of the chaser hurt because there is no part of separation that is fun to go through.
The runner does not mean to cause any harm or stress to the chaser and vice versa.
Some things that the runners say or do seem unforgivable but unconditional love heals all wounds — the runners finally come to their senses and ask for forgiveness once they realize that they have deeply hurt their Twin Flame.
Sometimes it takes a longer time for the runners to heal and make amends, and those with a huge ego can take longer to see the error of their ways.
All in all, unconditional love heals Twin Flames in many ways.