
I would say that I do it later, rather than sooner. And still my toy breeds leave home having played with Collies.
I use a whelping box inside a very large crate. Crate left open for mum to come and go, but the 4" lip doesn't allow my toy breed out for a long while. If a pup can't get out unaided, it doesn't get to meet the Collies. I let them progress at their own pace.
Although, to be fair, I have a breed that doesn't leave home at 7-8 weeks, so I can afford the time. They do get introduced to a couple of toy breeds at a time, but never before they are walking.