When I hear this type of contorted logic, the ideas of being "a little pregnant" comes to mind! LOL!!
No, if you know about the background, it makes sense.
Mortal sin breaks the relationship with God and sends the sinner to Hell. To restore the relationship, the sinner must confess and have his sin absolved.*
Being ex-communicated is a sort of public version of the above. Used to be that the ex-communicated could not go the Mass; now they are still obligated to attend while being refused the Eucharist until the sinner is reconciled with God, which might entail more than confession.
The main problem in either case is the state of the soul; ex-communication is just a public acknowledgement of this reserved for a very small number of sins.
*This does not mean the sinner gets off scott-free, only that his relationship with God is restored so he can eventually enter Heaven. There must still be reparation for the sin, either during the sinner’s life on earth or after his death in Purgatory, since nothing unclean can enter Heaven.