That finale (spoiler)

The two main protagonists would have been blown over and perhaps carried along for some distance from where they were standing when engulfed by the superheated cloud/wind/pyroclastic flow. They would not have been transformed into a kissing statue made of cinders -- childish, romantic embellishment, in keeping with the filmmakers' comic book style. I do give them points, however, for allowing the 'lovers' to die.