I'm looking at the chart and it does show that an Egyptian attack is 'Weak' against a Water-Nature opponent; I don't see where it says it should be 'Strong'.
Again, I'm looking at the chart on page 2 and your results are the same as what is on the chart; Against a Dark-Earth opponent Electric is 'Weak'
Water is neutral.
There are lot of columns so it's easy to get mixed up when checking it (I know I've put the wrong the result in the wrong column by accident before, lol).
Thanks for confirming this one!