Improper Map depictions

After loading a world in 20w17a, and opening a new map the map showed improper terrain (see "Example 1"); "Example 2" shows maps that were previously generated in 20w16a; and "Example 3" shows a side-by-side comparison of the improperly generated maP (left), to the correctly generated map (right); and "Example 4" shows a top-down view of the area both maps are depicting.