If you understand what the word should be and it’s consistently said, then I’d say it counts 😊 x
I was having a look online and things like ba for ball would count. At 15 months apparently mamma and dada plus 2 or 3 other words is normal. My boy says loads and clearly which blows my mind. Ball, get down, out there, eat, book, up side down, up, mama, dada, nana, rara, laura, Oscar, jojo, aunty. I've lost count and can't keep up. As well as lots of animal noises x
Baba ,da , ta , baba is bath for us lol help 🤣 but it's pronounced he lol
'Ba' could qualify as multiple words e.g. Ball, Bath etc... if said in context. No idea about how many they are expected to say by 15months.