How to reproduce:
1. Open the user’s attached “SplineOffsetBug.zip” project
2. Enter Play Mode
3. Observe the two cubes GameObjects

Expected result: Cubes are at different coordinates
Actual result: Cubes are at the same coordinates

Reproducible with: 2.1.0 (2021.3.25f1), 2.2.1 (2021.3.25f1, 2022.2.19f1, 2023.1.0b16, 2023.2.0a14)
Could not test with: 2020.3.48f1, 1.0.0-pre.8 (Errors after project/package downgrade)

Reproduced on: macOS 13.2.1 (Intel)

Notes:
Reproducible in the Editor and Standalone Player (macOS)
Not reproducible if selecting the GameObject with Start Offset in the Hierarchy window before entering Play Mode
In some editor versions, after entering Play Mode and selecting the GameObject with Start Offset in the Hierarchy window then, the GameObject jumps to the expected coordinates