Reproduction steps:
1. Open the attached “IN-117413.zip” project
2. Open the “SampleScene”
3. Enter Play mode
4. In the Scene view, switch to Wireframe mode
5. Observe that the “SplineSurface” GameObject has a deformed Spline
6. From the Hierarchy, select the “SplineSurface” GameObject
7. In the Inspector, in the Spline Container expand the “Spline 22”
8. Expand “Knot[0]” and observe the Tangent Lenght value

Expected result: The value is around 0.3 (approximately ⅓)
Actual result: The value is around 3.9

Reproducible with: 2.5.2 (6000.0.0b15), 2.8.2 (6000.0.60f1, 6000.2.8f1, 6000.3.0b6, 6000.4.0a3)

Reproducible on: Windows 11
Not reproducible on: no other environments tested

Note:
- Every other Spline without FitSplineToPoints has the correct tangent value