v/c ratio versus Lane Utilization Factor.

The guidance provided on page 10-26 of the HCM2000 is as follows:
"As demand approaches capacity, the analyst may use lane utilization factors closer to 1.0, which would indicate a more uniform use of the available lanes and less opportunity for drivers to freely select their lane."

In my experience, even under oversaturated conditions both approach legs and departure legs a traffic signal still exhibit unbalanced lane flow.

Unless there is a specific site characteristic that gives the intersection approach an unusual lane distribution, adjustments to any of the default modifiers for the ideal saturation flow rate are unlikely to introduce significant error into the LOS calculation.