Yes, they train full time. That's what a proprietary platform (not ours, third party, but hey, at least it has its own wikipage) will get you. Not even the build system is standard. Yes, they are paid salary. Very few people can afford to go several months without salary, that would filter out some candidates that proved to be right match in the end.
And that's the reason why the wage ramp up is slower, even after finishing the training.
That's a different situation then. A lot of companies make trainee employees sign a bond. To my knowledge all the Indian software consulting giants have one. If an employee leaves before the term is fulfilled (typically 2 years) they have to pay the company. It's usually on the order of 20-40% of an entry-level employee's annual salary. Otherwise the company can withhold references and experience letters, which are usually needed in future.
If you already have a bond/contract system in place and employees are still leaving, then IMO you're still paying them too little. If they are happy to pay 20-40% of their annual pay just to leave the company, it means they can make 50-100% more elsewhere. Loyalty is worth something but it's not worth passing up a pay raise that high.
And that's the reason why the wage ramp up is slower, even after finishing the training.