I think the article actually sort of addresses this, but only in passing and indirectly by mentioning that what they actually mean is growing up without breaste

I think the article actually sort of addresses this, but only in passing and indirectly by mentioning that what they actually mean is growing up without breastefeeding and with limited exposure to other children. When they say clean, they don't really mean how well scrubbed the floors and counters are. When these sorts of studies are coming out, they are very rarely talking about the cleanliness of the house, more so the lifestyle and habits of the occupants. Now there could well be a correlation between households that clean with cleaning agents and those that limit interaction and breastfeeding, but I do think it's very unlikely that that is what is going on.