There are records in the Ukrainian prosecutor's office, and statements on the record by his colleagues and deputies that he did nothing with the case. In 2015 he literally took 0 actions on the barisma case. Literally nothing. He didn't even touch the file.
His deputy (Kasko) resigned in frustration because Shokin made so little progress in the corruption cases he promised to pursue.
And he says there were no complaints about him... but he refused to assist the UK in a separate corruption case against Barisma... the IMF wanted him gone; the ERDC; the entire G7; and the Obama admin (not just Biden) because he failed in his job.
Shokin's statement (that you linked to in part) was made to help Firtash in a court case in Austria. Firtash is another Ukrainian energy tycoon being investigated for corruption, bribery, and money laundering. The fact that he's going to bat to help corrupt individuals avoid charges kind of says it all (the same people that as a prosecutor he would have been in charge of prosecuting--Firtash was also under investigation at the same time.. he did nothing on that case either).
parent quote source: https://www.youtube.com/watch?v=urTk6O4c0mU