Well if you're so familir with Leviticus so as not to need to read it again you know that 6:28 is a ritual observance and not a hygiene rule.
If the Egyptians were genuinely inferior to the Hebrews medically then you need to deal with their achieveemnts - not their mistakes. Remember that Galen and Hippocrates were not even born. Medicine had a LONG way to go.
And the fact is that many of the rituals do not have hygiene benefits. If some of the rituals happen to have bnnefits it does not mena that the creators of those rituals had knowledge of the health benefits. If the rule of 6:28 existed for the health benefits - as Grant Jeffrey says - then why was it not a general rule so that those benefits could be realised ? Obviously it did not.