Slaves and subs are human too. We all screw up at some point. So do Doms.
In long term relationships, even online only, I think it’s excessive for a Dom to release as well as punish. I bet those subs gave their all. They made a mistake, that’s all and would expect to be punished. They would accept the punishment willingly and probably never entered their mind they would be released unless they were continually breaking the rules, but not for a one time offense.
If both are as committed as they said they should be able to work things out. How sad that a slave gets released for being honest.