HDAdditionalLightData.RequestSubShadowMapRendering on directional lights breaks cascade shadows rendering

Steps to reproduce:

1. Open "OutdoorsScene" in attached project

2. Enter Play mode

Actual results: 

Cascade shadows other than the newly refreshed cascade are showing dark artifacts:

Expected results: 

Proper cascade shadows rendering similar to this : 

Reproducible with versions: 6000.0.1f1 (probably also lower, didn't test)

Not reproducible with versions: 

Can’t test with versions: 

Tested on (OS): Windows

Notes:

• The script InterlacedCascadesUpdate.cs does call HDAdditionalLightData.RequestSubShadowMapRendering sequencially for each cascade of the Sun light, with a delay between each call.
  It seems that only the first cascade doesn't have the issue.
• When disabling the script on the Sun object, and settings the Shadows update mode to "On Enable", and entering play mode, the shadows remain still while the light is moving, which is expected, but no dark artifacts are visible
• This is a critical feature required to save performances in a dynamic time of day scenario