As I understand it that's because the watch will prioritise GPS. Where GPS connectivity is inconsistent, it's possible to have the watch switch between the two. Given the purpose of the foot pod it to provide consistency it makes sense to have the ability to 'force' the watch always to use the foot pod data.
Some older Garmin devices did not have the option to select 'always' for footpod distance. It seems to me Stryd have updated their support article and have included the 245 in the wrong list.
Be aware that if you do select 'always' the displayed distance on your watch during your activity comes from the footpod but the distance written to the FIT file still comes from GPS.
Someone in the Stryd Facebook group has the watch and confirmed that you can set the footpod to “Always” without disabling GPS. So it should work the way the newer Garmin’s work with Stryd.
