140/400 is 0.35 still less than 0.5 of 4:2:2, so S-VHS with s-video on MPEG2 is still over kill

Kind of explains why HDV and D-VHS devices standardized on the MPEG2 digitization format with 0.15 overhead before reaching 4:2:2

They were much smaller than DV files or DV storage requirements, and still had far more chroma resolution. For that time.. they were future proof.

Only once the physical line lengths and aspect ratios began to change did they finally have to abandon the MPEG2 720x480x180 formats afforded by 4:2:2 for greater pastures.