I was surprised to find that the main concern is not structural damage due to a heavy landing (although that's a factor), but the ability to arrest descent and climb out if a go-around is necessary. Typically the narrow bodies can do it within acceptable parameters, but many widebodies can't if fully loaded and thus require fuel dump systems.

I don't know all the facts for this particular case, but it does seem odd that they didn't land anyway if they were having control issues.