One would think something similar would be expected from the hybrid image, without the need to extract those images.
It is beginning to look like a 'face-saving' stunt ....... as in 'oh yes you can now write the ISO to USB, all is great', but it has no real-life use, or very little.
It certainly does not appear to have any of the functions/facilities that are available by other means, so could not be considered in any way competitive with them.
Presently I can see it as a 'quick fix' to run an ISO on USB, but nothing else.
Maybe with better info it might be more amenable to general use ..... as in a USB drive to carry about, with persistence and easily changeable from one ISO to another.
Is it even possible to write an ISO to a stick without deleting all partitions and their contents?
16GB & 32GB USB sticks are common.
Am I going to destroy what I have set up on such a stick just to write a Hybrid ISO to it?
I am not, and I think that is its main problem.
That coupled with trying to set up persistence ..... where you have to (it seems) edit the boot options within the ISO first specifying your changes location which I guess could only be done by the use of LABEL, then convert it to hybrid and then write it to a stick, then set up a new partition for persistence with the correct LABEL, hoping that nothing else will have a similar LABEL wherever it might get booted.
Nothing about it is easy or simple, it appears.
Which is rather disappointing.