Thanks for the detailed response. This is what I thought, you and I are in sync, and the spreadsheet I posted at the beginning of this thread is accurate. WD does in fact transfer TW to the TT axles and therefore require less TV payload to support.
In your example, without WD requires 1000# of payload to support the TW load on the hitch (with 1500# on RGAWR due to front transfer). Then with WD, only 750# of payload is required to support the same 1000# of TW due to 250# being redistributed to the TT (not to mention more balanced F/R GAWR).
The only issue in my spreadsheet is that I don't point out the different areas where weight can be distributed with WD including; transferring weight to the TT, and transferring weight between the F&R axles. I only reflect the former and need to do a better job with the later. I will update it to be more accurate.
