Thanks for everybody's input. To provide an additional reason why lossless x265 is superior, Video A and B are presented for a trivial scheme : interweave.
First, interweave both video; Second, select and mux the even frame; third, compare it under PSNR measure.
Video A:
https://www5.zippyshare.com/v/uVQP4Ccc/file.html
Video B:
https://www87.zippyshare.com/v/pkkl1Eph/file.html
x265 crf 0 interweave scheme
ffmpeg -i in.y4m -i out.y4m -filter_complex framepack=frameseq -c:v libx265 -crf 0 output.mp4
ffmpeg -i output.mp4 -vf select=mod(n\,2) -r 24000/1001 -c:v libx265 -crf 0 output1.mp4
ffmpeg -i output1.mp4 -i out.y4m -lavfi psnr=stats_file=psnr.csv -f null -
x265 lossless interweave scheme
ffmpeg -i in.y4m -i out.y4m -filter_complex framepack=frameseq -c:v libx265 lossless=1 output.mp4
ffmpeg -i output.mp4 -vf select=mod(n\,2) -r 24000/1001 -c:v libx265 -x265-params lossless=1 output1.mp4
ffmpeg -i output1.mp4 -i out.y4m -lavfi psnr=stats_file=psnr.csv -f null -
raw lossless interweave scheme
ffmpeg -i in.y4m -i out.y4m -filter_complex framepack=frameseq -f yuv4mpegpipe output.y4m
ffmpeg -i output.y4m -vf select=mod(n\,2) -r 24000/1001 -f yuv4mpegpipe output1.y4m
ffmpeg -i output1.y4m -i out.y4m -lavfi psnr=stats_file=psnr.csv -f null -
A mean-square-error of 0.00 but PSNR of non-inf is quite surprised me in the crf=0 x265 scheme.
Maybe there exists some bit-exact-accuracy options I didn't activate for x265, but crf=0 is definitely not lossless.
Out of topic
x264 crf 0 interweave scheme
ffmpeg -i in.y4m -i out.y4m -filter_complex framepack=frameseq -c:v libx264 -crf 0 output.mp4
ffmpeg -i output.mp4 -vf select=mod(n\,2) -r 24000/1001 -c:v libx264 -crf 0 output1.mp4
ffmpeg -i output1.mp4 -i out.y4m -lavfi psnr=stats_file=psnr.csv -f null -