How to reproduce:
1. Open the attached project "StyleKeywordInitial"
2. Go to Repro -> Run Bug 03
3. Observe the two parent/child pairs in the Game view for the first 10 seconds
4. Observe the results after 10 seconds, when the bottom child has StyleKeyword.Initial applied from C#
Expected results: The bottom child keeps conforming to the parent's curve, because the initial value of -unity-curvature is "none"
Actual results: The bottom child renders flat and opts its own subtree out of the parent's curve, because StyleCurvature(StyleKeyword.Initial).value returns Curvature.Initial(), which is an explicit "0deg 0deg" value (IsNone() == false) rather than Curvature.None()
Reproducible with: 6000.7.0a6
Can't test with: 6000.3.17f1, 6000.5.10f1, 6000.6.0f1, 6000.7.0a5 (No such property)
Reproducible on: Ubuntu 24.04.4 LTS (Intel i9-10980XE), macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested