You are correct. You can’t really turn the ordinal stuff into a cardinal ordering, just into a kind of proxy ordering that has some cardinal structure, but it might not correspond to the cardinal structure we care about. For example if ‘perfect health’ was added and 100% of people ranked this above the other choice, then it would end up very far (possibly infinitely far) from the nearest option on the cardinal scale. What it is really measuring is the amount of disagreement about things at this part of the ordering, which is a proxy for closeness of the health levels, but there are cases like ‘perfect health’ vs slightly worse than that where they are close but there is no disagreement.
You are correct. You can’t really turn the ordinal stuff into a cardinal ordering, just into a kind of proxy ordering that has some cardinal structure, but it might not correspond to the cardinal structure we care about. For example if ‘perfect health’ was added and 100% of people ranked this above the other choice, then it would end up very far (possibly infinitely far) from the nearest option on the cardinal scale. What it is really measuring is the amount of disagreement about things at this part of the ordering, which is a proxy for closeness of the health levels, but there are cases like ‘perfect health’ vs slightly worse than that where they are close but there is no disagreement.