I understood this too, from @LGBX article posted. But now I wonder what Jake (the author) wanted to say with the 2nd point highlighted also by LGBX.
->> 2. Rewards earned from delegating on Daedalus Shelley Testnet are not redeemable and was intended for testing purposes only.
I guess this applies to rewards assessed to owners of the pools after functioning of ITN has been prolonged for one month at the end of June. This issue was discussed at that time and there was the voting among ADA holders about it but I didn't take part in it.