Well, that's more of an interpretation rather than what the sentence really says.
Is powinna pronounced correctly by the digital voice? It sounds like "powinana". It should just sound like "powina," right?
It's still confusing. The first pronunciation of the three links pronounces it with the two Ns separate, like poWInyna, and the other two pronounce the double N as one, elongated N sound. Then, with wanna, two of the pronunciations separate the two Ns, sounding like WAnyna, and the other ones pronounce it like one, elongated N sound.
In Russian we also have ванна ("wanna") but the two Ns are never separated into ванына
Yes, the first "powinna" sounds strange. It should always be a double sound without any schwa or any other vowel in-between. As far as I know, identical to Russian.