I honestly doubt that it is a 128GB M.2 SSD in that. Just like most other sales I’ve seen like this, it’s probably 64 GB eMMC + 64 GB M.2.
If this is the case, I wouldn’t. The M.2 is a nice addition, but you would be better off buying one on your own, since it will most likely be slow as hell compared to what you can get on the side for not much more $$.