OK. I am an idiot. The method above does solve the problem of the base install of libreelec/KODI (12.0.0.0) not expanding the STORAGE partition on install with large disks. I mis-typed the new UUID in the cmdline.txt by one character and even though I double checked it, I had should have triple checked it. So process to fix STORAGE partition size on large disks after install is:
1. Create Gparted Live bootable USB and run.
2. Run Gprarted and attach libreelec drive you used somehow.
3. In terminal, use mke2fs to change the block size of the STORAGE partition to 4K (4096 bytes) -or- you could probably blow away the original STORAGE partition and recreate it using Gparted graphical interface.
4. Properly note the new UUID of the STORAGE partition as changing block size or recreating it will chnage UUID.
5. Edit the cmdline.txt on the LIBREELEC partition with new UUID.
6. This means change this part of the command in the file to:
There are probably other ways to solve this problem but this has been my journey.