Law /
Why does Poland not have a repatriation office? [38]
The Polish government uses it euphemistically
Nothing 'euphemistic' about it. Those people are usually descended from people deported during the war to Kazakhstan etc and unable to return.
prove that your Polish ancestor didn't do something that would have resulted in a loss of citizenship under the 1920 Polish citizenship law.
It means that if someone revoked their Polish citizenship, had it cancelled by the Polish government or had it revoked on their behalf by a parent or guardian, that is permanent. Anyone in that situation must apply through the normal channels. Many do.
ALL Polish citizens who were living abroad before
Why would their descendents need any special help to gain citizenship? If they wish to reside in Poland or any other EU member state, the normal immigration laws should suffice.