Very strange indeed, I’ve had quite a few of these over the years without any firmware issues, but there’s always a first!
No you shouldn’t have “firmware” at all, I can’t recommend HiPro over the iCube ll, but if your happy to use cables then go for it.
You don’t need or want target 8.1 for those old V70’s, you could just use 6 or 5.
Just be sure to get the right cables CS44a for Phonak.