Insurers will assume 100% loss for these structures (always assuming that they can recognise them, which is a real problem in many cases). This estimation process is often a little pessimistic, but not for this construction method, IMHO.
It will be relatively easy to construct a SIP that will pass the current tests: not least because currently the wall/ceiling junctions are not tested. This is where I would expect real weakness.
The structures are likely to be deteriorating, at least in fire performance terms. throughout their lives, not only as adhesives/foams etc age, but also as a result of ordinary human occupation. These buildings have a lifespan. Would you buy one that was thirty years old?
The lifespan issue isn't necessarily a problem, provided everyone is aware. For commercial buildings, where the cost can be amortised over the lifespan, no problem. Potential owner-occupiers may wish to consider the longer term, however.
Incidentally, much of above is true for other 'Modern Methods of Construction'.
And don't get me started about MMC fire performance during the construction phase. I didn't see much comment on this forum about the fire at Colindale a few months back, which surprised me. That was scary!
All above opinions my own, of course.
