Isn't there a slight difference in meaning, Glen?
If only he had apologised to the manager...
This version expresses regret that he didn't apologise. Compare with "If only I hadn't thrown the lottery ticket out with the trash...
Only if he had apologised to the manager could he have started work again.
I take that to mean "If, and only if, he had apologised to the manager, he could have started work again."