Oh don't get me wrong, I'm sure it is very real and I do agree with you that there are many many people who can barely raise one dog correctly (even if they think they are doing a great job). I know a few of those people and just want to hit them over the head and say..what are you thinking? Yes, it's a dog, but it's also a family member/child!!!
I took great care of my previous boxer (Buster), even though I was with him for the last 2 years of his life. I always made sure he was well taken care of (mentally, health wise, exercise, etc..) I did everything I could for him and fought for him til the very last breath he took. That's how I am and plan on raising my 2 pups.
I understand that the authors aren't implying to have the dogs live completely separate lives, but it probably comes off that way to a lot of people and thats why they don't separate the dogs when needed.
There are way too many people out there who think "oh let's get a puppy..they are so fun" and in return don't take care of it like they should..I'm working very hard with my 2 puppies and yes it's a challenge, but if I didn't think I would be up for it, I wouldn't have taken in both, I would have only gotten one. I work with both of them separately and together, depending on what it is and how they act. Training (sit,stay,come, etc..), I do separately so they learn for themselves and not from each other. I'm proud of them in how much they have learned thus far and know that they will be great dogs when older!