As any driving instructor will concede, rules change and re-thinks are constantly applied. The 1960 (UK) Highway Code rules have since been modified in line with common practice - and commonsense. So if I were to apply the 1960 rules today I would not get through my test. BTW. I seem to recall that the Highway Code in parts was advisory, not a legal requirement. Perhaps the same for its Spanish equivalent?
Most of us are well aware that in Spain the driver on the kerbside lane is correct to continue to circle the roundabout. However, when they do so they cause many near accidents when the vehicle nearest the roundabout wishes to continue up the main carriageway.
The fact that this or anything else is in the Spanish or any other Highway Code does not necessarily mean it is sensible practice. I think in time this rule will be modified, as in the UK.
Commonsense, the survival instinct would never allow me to continue around a roundabout if I suspected the truck on the lane nearest the roundabout was likely to cut across my bows. Try telling my corpse that I was at least in the right according to the Highway Code. I recall a driving instructor telling me that if everyone drove according to the Highway Code there would be gridlock. There isn’t because drivers, when commonsense prevails, disobey the advisory rules.