I spoke to the representative that came to explain the ERC to me, he's the guy that supplies the Precice to my doctor.
Even if you are light-weighted, he explained to me that the Precice was not conceived to be weight-bearing while walking. From his explanation and from my understanding, it's that the movement, pressure and weight caused by walking will bend/break the nail, or cause damage to its lengthening mechanism. It's as if you were holding a pencil with your two hands at each end, and applying pressure to the center with your thumbs. Plus, you're putting way more than half your weight when walking.
So you can't walk without assistance (crutches/walker) with the Precice. You can only walk without assistance when your doc says so, according to the X-Rays etc., so when your bones are almost completely healed.
If you're looking to walk sooner without assistance, the Precice Max is supposedly coming out this winter 2023 in the US. It will be supposedly weight-bearing, more resistant, and fixes some the weaknesses that the Precice had (in regards to breakage in rotation, bending, etc.).