The USB is not the live Fedora image. The USB is a pair of partitions, one of which contains the live image. That is a big difference. It is not a bug in Anaconda. You can’t expect Anaconda to have a detector for Ventoy, just to avoid offering the Ventoy media as an option for the install destination.
I have run Anaconda from Ventoy several times and it always offers the USB stick as an install destination.
As I said earlier, I don’t know what the Free up space check mark in that GUI actually causes to happen. The one time I tried that checkbox myself, I couldn’t get it to work. Without that, there was under 1MB of unpartitioned space on the Ventoy stick. Anaconda would have no use for that 1MB. Unless it really acted on the Free up space selection, telling it to use both would mean telling it to use only the one on the left.
What exact size is that? Do you have a URL for the technical specs for that SSD? Is it really supposed to be that much more than 1TB? (Or are you still ignoring the meaning of GiB).