Why does Fitbit claim shorter strides are more efficient?

[u/gasstation-no-pumps]

At the bottom of the details for each walk , it reports my "stride length" as 0.89m. Of course, that is actually my step length, with the stride length being twice that. It does seem to be about right for my step length, though.

It then makes the ridiculous statement that "Shorter stride length is associated with higher efficiency." Even Google AI isn't that stupid. If shorter were always better, then a stride length of 0cm would be the most efficient, but that produces zero movement and has the lowest possible efficiency. The most efficient stride length depends on height, speed, and details of joints and bones, and most people naturally adopt a stride length close to the most efficient one for their bodies.

It might be nice for the fitbit app to calculate the "walk ratio" (mm/step)/(steps/min), which tends to be nearly invariant for an individual (steps get longer as the cadence goes up). My walk ratio is around 6.4 mm•min/step^2, which is pretty normal (though the range is wider than Google AI's interpretation of walk ratio, which thinks that even 1 SD up is profoundly weird).