I am going to ignore all of the Fit1/2/3 stuff from Bauer and just focus on standard D and EE fits for simplicity skate. When you go down a half size from a 6, 7, 8, 9, 10 size skate you usually end up with a smaller holder.
This gets even more complicated when you add width it's the equation. Example:
Bauer 6.5D = 254
Bauer 6.5EE = 263
Bauer 7D = 263
Bauer 7.5D = 263
Bauer 7.5EE = 272
Bauer 8.0D = 272
Bauer 8.0EE = 272
Now imagine you wear a Bauer 7.5EE and therefore skate on a 272 holder and now need a size 7 or smaller TRUE skate. You would be going from 272 to 263 or a 254.
Let's take this a step further. Imagine you are going from a 7.5EE Bauer to a 6.5 TRUE skate, you would be going from a 272 to a 254.
Does this make things a little more clear? Perhaps clear as mud in some ways. Let's please not get CCM and Mako sizing added to this as well since that in itself is a whole other can of worms.
With all of this being said I really wish that manufacturers would all standardize skate length and holder sizing, but that is likely not going to happen in my lifetime.