I'm sure he'll share his explanation of why he chooses to do it this way but in general with females that have just laid, any hit of the sent of their eggs supposedly can cause them stress and an urge to find their clutch and continue to incubate them instinctually. So they stay in new mother mode instead of moving on to feeding. I have not experienced this though, washing with water has been enough for my girls to forget about the eggs and resume feeding.
I have had a few look for their eggs for days. I had one incubate her water bowl and went on to not eat until awhile after her clutch actually hatched. Since then I clean really well.