I am in a lot of parenting meet up groups, and, in my experience, every parent's children are "delayed" in some area.
For example, our neighbor's son is a very social kid, and he has been able to hold conversations with adults since before he was 4. He's also very athletic and a competitive kid. He loves to run and make things into games. But the teachers tell his mom how he is delayed in his fine motor skills. They don't say, "Hey, before kindergarten, it would be helpful for your son if you practice some games that will utilize his fine motor skills." Nope, they point out how he's delayed. It's annoying, imo.
My son is doing well academically, but emotionally he is a bit immature. At school, when he gets upset, he'll just lay down on the floor and doesn't want to do anything. The teachers tell me that he's emotionally immature and might not be ready for kindergarten, but in their next breath they tell me he shouldn't be held back because he'd be bored in school and might act out more.
Oh, and my daughter, who is 3, goes to class in a 2 year old room a couple hours a week (she was 2 at the start of the school year). Her teachers tell me how she shows a delay in her gross motor skills because she won't kick a ball and won't go down the slide.
My opinion is, why does everything have to be a delay? Kids don't all develop in the exact same way at the same rate. If your friend's child is progressing in his speech and isn't frustrated in his ability to communicate and doesn't seem to be delayed in other ways (ie., the delay isn't autism), then I wouldn't worry too much about it if the mother and doctor aren't. My son didn't speak in conversations until he was 4.5. My daughter, who is 3, speaks almost exactly like your friend's son. If I ask her if she would like me to pick her up, she'll answer, "Pick you up!" She communicates what she wants and needs, but she isn't able to have a conversation yet. I'm not worried because she's clearly not delayed intellectually or emotionally, so I know it's not because of an undiagnosed disability or autism or something. She'll just get there when she gets there. It reminds me of something my grandma once told me. She had 9 kids. Her 3rd child didn't really speak at all... until her 4th child started speaking! Speech delays can be a sign of a bigger problem, but they can also just be a kid just not quite as verbal as the average child that same age. Some normal kids don't walk until they're almost 18 months old. Some normal kids still poop their pants when their 4. I think rather than always worrying parents that there's something wrong, just let kids be individuals.