[renowner]

I still believe its unintended based on the update notes describing flanking over the years.
They all say that flanking is halved if no ally is also near the enemy, and halved again if you don't attack from behind.
This implies that X is supposed to always be half, not only the original half, which the tooltip also seems to corroborate.
(I also see no update since then describing any changes to guile.)