I've had two emails since yesterday's post, this a reply to them both.
When I came into the sport in 1956, cross country courses were laid by the host club around the countryside where they were based. If the trail included hills you ran over them, the natural route through a field was taken and at times this meant climbing gates (which were never opened) or crossing streams. 'Reading' the course was a skill and no cross country runner would race without first jogging over the trail to see the layout and problems presented by that particular course. Ian Donald in our club was the best reader of a course that I ever saw - there was one race at Milngavie where a narrow path led across a field to a two feet high stone wall which had a six or seven foot drop on the other side - not having had a look you might well have seriously injured yourself. Ian had a look, tried a couple of approaches and decided to cross a few yards to the right of the path where the take off was firmer and the landing was better and where other runners would probably be away to your left giving you some space. The courses required skill to run.
Then in the 60's the authorities decided to follow the continental example and use flat, fast runners courses. Jim Hogan was disqualified in an international race in Wales for running between the steeplechase barriers that had been placed as obstacles. His defence was that you could negotiate obstacles in cross country by the best means possible. The Scottish National was held at Duddingston one year with steeplechase barriers out on the course; when one was knocked over on the first of five laps, an official was placed by it to tell runners to jump over the neighbouring barriers which were still standing. No one bothered with him.
But at least they had obstacles in the way - even if only steeplechase barriers. Trails now don't even have these! The reaction to the golf courses was for organisers to make up so-called tough courses. But fences, streams, ditches, obstacles of any kind are out of order. To be traditional, the courses would have to have gates not open (unless they were open at all other times), streams or ditches to cross, difficult obstacles (such as the one at Milngavie described above) and follow a natural route. If such a trail were laid, then it would have to be modified for the younger athletes - and that would probably mean making it easier undefoot and removing awkward obstacles - it would not simply mean giving the same as adults but slightly less of it. Good trails to me are the kind you get in Ayrshire with mud, rivers, and so on. You need a particular skill to run them.
Trails like Kirkie had not a single obstacle (perhaps because it was thought too risky on the grounds of health and safety!) and a running surface that was guaranteed to produce a whole series of ankle and knee injuries. So my answer is that traditional trails had a variety of challenges that required and rewarded skill with different courses for children, not just shorter ones.