It's simple
JYP Entertainment gave TWICE "fake" solo activities hidden under melody/performance "project" names.
With that TWAISU division is tricking girls that everything is NAISU, and not only they have group activities but also solo/duo ones. Then they will happily re-sign contracts for the next 4-5 years.
After that JYP ahjussi will come wearing some fancy hat and will say that they have tons of work to do 2 Korean, and 2 Japanese comebacks per year, but of course if they want they can also continue their melody/performance projects 
And that's a neverending cycle of life.
