When my handlebar was only 1-2 cm lower than my saddle on my long distance bike on long rides my two fingers on each hand would go numb. I think it was easier for my body to be rested on the hands to pinch nerves in my hands because of too much pressure.
I was aware of the issue, but it was hard to use my core mussels and not rest on the handlebars when I was tired after long rides (600+ km) . Raising the bar would make things worse. I would lean ("rest") even more on the bars plus my neck would hurt also.

To fix it , I lowered the handlebar even more ~10 cm and used a -17 degree stem to be more stretched. It forces my core mussels to work more and hold my body and not "rest" on the hands as much.

I do not have the problems with numb hands on my other "race" bike, since the bar is ~12 cm lower that the saddle. I do not rest on the bars as much, my hands just rest on the bars with very slight pressure.
My core mussels work more on my "race" bike, but I have no pain in my hands. I am trying to set up my "long distance" bike almost like my "race" bike, but the headtube is too tall. Have not done a 600km ride since the -17 stem was installed on the long distance bike, but so far so good.