The latter bit isn't true; current Chrome OS developer firmware will allow
you to boot any developer-signed USB stick.
But it is true that these have to be laid out so that the Chrome OS firmware
understands them, which means EFI, the particular GPT layout, etc. not as a
standard El Torito image or similar. So creating a hybrid image is going to
be very very hard indeed.
The latter bit isn't true; current Chrome OS developer firmware will allow
you to boot any developer-signed USB stick.
But it is true that these have to be laid out so that the Chrome OS firmware
understands them, which means EFI, the particular GPT layout, etc. not as a
standard El Torito image or similar. So creating a hybrid image is going to
be very very hard indeed.
Scott