I have to agree with the post starter, i also noticed that if you enchant items for a long period of time (hour) there is an small space of safe enchanting (longer than 15sec, omg) but not like 10mins.
I noticed it in L2fea kamael server, it has high enchant rates, but getting +16 weapons was difficult too, and in the safe enchant period i could do 2 in a time from +0, and then broke all the others before +10.
BTW, there are and have been enchant exploits, its not a myth, i have enchanted safely in l2forfun server (interlude) using l2phx and warehouse, without any script, just 3 lines to send.