WDP don’t know because fuel is not saved in the file that WDP reads. You can see for yourself if you save a BMS session and load it again your fuel (and LGB PRF code) are lost. The performance section doesn’t let you input fuel because it’s take off data so full fuel (-taxi) is assumed. As for the right hand pane and other pages, those calculations are GW-invariant.
If you really want TO data at a particular fuel level set the taxi fuel to the appropriate amount.