We're talking about different age ranges here. For 0-3 years, especially infants, the attachment research is very consistent primary caregivers matter enormously for development. A 1yo doesn't need to "expand their social life" they need secure attachment. The socialization benefits you're describing kick in later, around 3-4 years old.
Daycare typically won't take a kid until potty trained, so at least 2 and a half or so. At the early ages, it's only a few hours a day as well in my experience.
