Empty waterbody file in non-coast line area

[mcmjasir]

Hai everyone,
I created a wbd file for alos2 processing using wbd.py command but I find that the output (.wbd file) contains zero values only ( first figure).
But when I created an wbd file for the coastline area I can see the water bodies in the out file (second figure).

I am wondering what was the reason for this difference and what will happen when I use zero wbd file in my alos2 insar processing ?

I used offline data from http://e4ftl01.cr.usgs.gov/MEASURES/SRTMSWBD.003/2000.02.11/ because my work station is not connected to internet .
Thank u in advance .