Didn't know caravans would run without a battery in place - acting as a large capacitor to smooth the output to 12v outlets. I would be concerned about 'spikes' in the voltage of supply using the Nordelectronica as a transformer. However 10 years is a long testing ground!...
I can't tell you when it became common for caravans to be fitted with battery chargers for the first time, but they were just transformers and rectifiers, and did not have smoothed outputs. They could easily produce peak voltages of 21V and as such they needed a battery to help smooth the ripple. A battery was essential to protect some of the caravan accessories of the day.
Since the mid 1980's, UK caravans were fitted with regulated 13.8V power supplies, rather than just battery chargers. They generally had about an 8A capacity which would run some of the caravans systems but by them selves, they sometime struggled or even failed to run the water pump, so a battery was usually still required to meet peak current demands..
Being regulated to 13.8V they could be used to charge a battery and left connected during the holiday to keep the battery topped up.
Later units often have current capacity up to 16A. These bigger units could run a whole caravan, but sometimes you need to be selective about what appliances you used at the same time, so a battery was not essential but advised.
The most recent power supplies do more. They are still limited to under 16A, but some have a smart charging facility.