That's something I've often heard, the fact that the device could generate a weak electrical field is merely incidental. I find that idea to be quite credible, given that even if it were designed to generate some electricity, there is nothing of which I'm aware in the Sassanid material culture to which it could've been applied.
I admit that the Baghdad battery is not something I've ever bothered to study beyond casual reading. The Sassanid culture is beyond the period of history in the Near East, and particularly in that area of the Near East, that I could identify as my forte. The Persian empire? Certainly, but a modest pre-Islamic culture of the early centuries CE is somewhat beyond my sphere of interest.
Still, an artifact like this one needs to be studied not as something separate but as something that was a part of the culture to which it belonged. And it does not appear that the Sassanids had any keen interest in electricity.