You're right, but its the standard that everyone has converged on. The assumption is that it is for lithium ion chemistry which is nominally 3.7v I don't know

You're right, but its the standard that everyone has converged on. The assumption is that it is for lithium ion chemistry which is nominally 3.7v I don't know if this is going to frustrate you more, but I recently needed a small battery so I picked up this unit[0] at walmart, where it came rated in mAh for both 3.7v and 5v. The battery itself also has WH marked on it. A step in... a direction I guess [0]https://www.walmart.com/ip/onn-Portable-Battery-4k-mAh-Black/934734622?athbdg=L1600 https://www.walmart.com/ip/onn-Portable-Battery-4k-mAh-Black...