I have attended 6 different TTT classes over the years. All of these classes were 3 day. Most offered by fork vendors. The impetus for my instructors and I to attend these classes have been to deflect liability and provide proof of qualifications. From the employer's point of view, It really comes down to compliance for the company.
In the depositions I have been to, the attorneys wanted to see the curriculum that the student got from the class, videos etcetera. And then they wanted to see the curriculum I received at my various TTT classes. Documentation goes a long way. We have been fortunate to have the number of hours worked with few accidents.
I have seen online TTT programs that claim the requirements for instructors is somewhat less now than in the past, so if the company's loss prevention dept believes what they read online they can save$.