Step geometeries in sftraj objects are linestrings going from t1 to t2 of a 'step'. As these are stored at the row level they are not dynamic to changes in t2. step_recalc allows you to recalculate these geometeries if your data.frame has changed because of subsetting or filtering.
step_recalc(x, return = FALSE)an sftraj object.
return step_geometry instead of replacing sftraj object with new step geometry. Defaults to FALSE