I got my numbers mixed up. It is physically smaller in the long direction, but bigger in the width direction. I don't think it will fit in the Pro1 enclosure. It might still be usable to power a Pro1 if the original battery dies, but it wouldn't work with the phone all put together. We'd need a battery that is long and skinny, like the Pro1 battery, and then convert the cable to the right connector.
This explains how they were able to cram so much power into such a small battery. They weren't! 🤣