HSC-I2 SKY images actually come from those constructed from 202101 run data. This is because almost all the science in this run are suffered by nearby very large galaxies. 

HSC-Z SKY images are not of very good quality, but we consider acceptable for general use. 

HSC-Y SKY images were actually constructed from not only this run data but also the other observing runs data (202012^202106). This is because of a small number of the available data in this run.