Apple Watch different running distance for same route

Hi Apple Community,

My partner and I both have Apple Watch Series 8 (no cellular), and we often run together, and usually side by side. However, I’ve noticed that my watch consistently records about 300 meters more than his, even when he sometimes runs further and then comes back to my side. We’ve checked our calibrations and personal data, and everything seems fine.

Has anyone else experienced this issue or have any suggestions on how to resolve it?

Thanks in advance for your help!