Certainly it's not "baby language" but sometimes we should encourage to make an effort in order to understand a simple idea.
By the way, babies also profit from clear simple concepts, they don't need to be talked to in a "completely different language".
Prof. Erika Hoff, a developmental psychologist at Florida Atlantic University, said parents should not restrict their conversations to simplistic baby talk. Rich and complex language, with adjectives and subordinate clauses, helped them to learn the complex structure of language. "Children cannot learn what they don't hear," she said.
Source: Talking to babies boosts their brain power, studies show