tunixgud This happens with every series: the first episode as selected,
and all the others in maximum quality/size.
I cannot confirm that as universally valid ..
I tried Task and selected s01e01+e02 with 2nd HDR10 4k offer (5.2 GB):

and I get ep2 also in 2nd HDR10 4k offer (4.4 GB):


But highest HDR10 offer for ep2 is > 8 GB (checked with Movie Mode)

=> So it’s definitely not the highest quality for the same resolution.