To me, it means that the mechanics didn't work very well. Several of us have examples laying around, I'm sure. I remember designing stuff like a CrIg fireball to target the British isles in a single hit, because of how T:Boundary was written, or a starting character who was able to mass-produce flying castles, as long as he had the Vis.
Also, Concentration quickly becomes the most valuable skill in the game, because it adds to the XPs you get per season when you study from books, IIRC (@Christian_Andersen please correct me if I'm wrong).
Essentially, in the first 3 editions, libraries were much simpler, and there were no guidelines per se - each troupe were expected to eyeball spell/effect levels by comparing them to other spells/effects in the game. Also, Arts were explicitly not associated with XPs (something I miss, though I realise I may be the only one).
Then 4th edition came about. And to be honest, it felt like a mess. To me at least.
I would like to point you to this thread: Little Things I Miss From 4th
To be honest, I'm currently unemployed, and my first thought to your original thread was wondering if I could somehow arrange to buy you a (digital) copy of the 5th edition.