It’s often the case that a signing baby uses the same or similar signs to mean different things. As your baby develops, his motor coordination is constantly paying catch up to his desires. However, signs that appear similar shouldn’t be thought of any differently that signs that appear the same. In other words, even though your baby does the same or similar motion for multiple words, it doesn’t mean that he thinks they are the same thing. Your baby understands the difference in the worlds, he’s just not signing (saying) it properly. To him, he’s saying two distinct things even when he’s signing it similarly.
This is the same thing we see when babies start to talk, but their words come out sounding alike. This means, you shouldn’t worry too much about signs appearing similar, just be sure to model the correct sign back to your baby so they eventually refine their signs to the proper “pronunciation.” With time and practice your baby will become more coordinated and will sign the words with more clarity. The same evolution as to what happens with spoken words holds true for signs!