Part 135 Credit For Previous Training

Does anyone know where I can find specific guidance regarding giving credit to a new-hire for previous training received under 14 CFR Part 135?
Part 135 approved Training Programs that I have worked with in the past had four different classifications of Initial New Hires (INHA, INHB, INHC, and INHD) based on their previous experience.
I have gone through the 8900.1, but I cannot find any guidance for these four classifications. In fact, the 8900.1 appears to now treat everyone without previous experience with the operator as the same. That is, there appears to be only one classification of Initial New Hire in the 8900.1 regardless of previous experience with another operator. This would imply that a New Hire with extensive previous 135 experience, including experience in type, would have to go through the same Initial Training (including Indoc, Aircraft Ground, Aircraft Flight/Sim, etc.) as someone with no previous 135 experience & no previous experience in type.
This doesn’t seem correct. Am I misinterpreting something here???
Please respond with specific references to 8900.1 or other official FAA documents (Orders, Notices, ACs, InFOs, etc.).
Thank you!

I do believe that all training must consider that every pilot has no clue as to the regs. Must be an FAA thing because 135.329 does not talk about anything being transferable.

Talk to your POI- I was working for company A when Company B in Alaska offered me a ton of money to come work flying the same AC. Company A allowed me to take 4 months off to work for company B.
The POI allowed all previous training Aircraft specific to count and all I had to do was spend a day going over the GOM and, we did a 135.297 and blam I was flying the line.