Theres no one-rule-fits-all when it comes to overtraining imo, everyone is different. Bottom line is that everyone will adapt, eventually.
The reason my max-squat every workout program failed was that i didnt have time to eat and sleep in sufficent amounts, for example.
Check out this article, i thought it was quite spot on when it comes to "overtraining".
Squatting Every Day and the John Broz Training Method