You Can Only Teach a Service Dog Three Tricks?

So says the trainer with the service dog program I am considering working with.  I spoke to her by phone today to set up a time to go visit the program and see a couple of the dogs nearing the end of their training, which I think I will be doing on Friday.

But she also wanted to talk to me about my application and the tasks I'd mentioned I wanted a dog to be trained to help me with.  I listed six or seven things on the application and she said I need to narrow it down to three.  She said they usually only teach the dog to do a maximum of three tasks because if they try to teach the dog more than that, the dog gets too stressed and is unable to become proficient at any of the tasks.  So she told me to look at my list of tasks and decide which ones I think are most important.

I've never heard this before and I think I've done a fair amount of research.  I was in the car on my way to the Cleveland Clinic to see my back specialist when I was talking to her (I know, you're not supposed to talk on your cell phone and drive at the same time, but it's a long drive and it's boring and it's so convenient to make phone calls while I'm in the car) so I just said OK.  I couldn't wait to get home so I could get online and ask some people if this was correct, if service dogs were usually only trained to do three tasks.  Because it doesn't sound right to me.  I am really not sure about this program.