An evergreen discussion topic this.
There are those who interpret the 249 NM as referring to the geographical segmentation of the wind update, i.e. same winds applied to all waypoints within the 1st 249 NM on the route, then the next wind for the following 249 NM etc.
This instead of LIDO providing more accurate individual wind data for each waypoint (with less than 249 NM apart).
I.e. nothing to do with any winds being updated automatically (requires an execute on the FMS normally as we all well know).
Check next time when performing an update like this.
Would like to get the full explanation from the source myself as well though.