This post has been escalated to our Support team. If you have a similar question please submit a support ticket and we will investigate further.

UPDATE FROM SUPPORT: Our team found that there is limited distance data that is being written in the files which led to the distance being shortened when they sync to Strava. 
 
In the meantime, you can swap your distance stream on your activities to instead calculate the distance for your snowboarding activities using the GPS data.
 
To swap your distance stream:

• Go to your activity page on the website (this feature is currently not accessible in our mobile apps)
• From the activity page click on (◦◦◦) the more options menu > Correct Distance.
• From the pop-up, click "Correct Distance".
• When the status changes from "Calculating" to "Updated," refresh the page.

If you would like to revert the change, you can click the same link and click "Revert Distance".
 
For more information, see our article on How distance is calculated for your activity. 

Our engineers are working with Google to make improvements to the distance recording for activities on the Strava Wear OS watch app for Pixel watches. They are hoping to have it updated in the near future which will improve the distance recording functions on non-run and ride sport types on the pixel watch. In the meantime, you can continue to use the "Correct Distance" option to swap the distance stream on your snowboarding activities to use the GPS-calculated distances.