OK, to be more explicit:
If the washing powder or liquid has any whiteners, brighteners, bleachs, enzymes, 'fresh smells' or fabric softeners, it is very likely to leave a residue on the fabric. These will all sabotage the DWR by hacking the surface tension of the DWR coating.
I note Richard's comment about the Gore instructions. Frankly, I would contradict Gore myself. In my experience, most powdered washing stuff has some of the above nasties, and you can check this by reading the packet. On the other hand, the Sports Washes from good outdoor companies are all liquids and they do not have the nasties - by careful design.
Personally, I use the Atsko stuff, because they have lab testing to support it. I do not know about the others.
That said, the 'double rinse' instruction is good. Make d@mn sure you rinse every last bubble off the fabric. That also goes for any down gear.
Now, rather than trust me, try:
You might also like to know that so-called flammability treatments (eg for tents and clothing) are both toxic and ineffective. The whole flammability thing is a scam run by the companies who make the chemicals. The results from the only research ever done have been seriously misused by chemical marketing and disavowed by the researcher involved.