JP1 Remotes

I need a high level explaination of why upgrades seem to define functions for a new device instead of moving buttons on the original.

For example, when one loads the Tivo_Master file the functions are associated with the VCR device. Why place them there instead of the SAT device?

Becuase TiVo is a VCR, essentially. There is no reason not to assign it to satellite, if that is what you want to do.

It really has to do with the default "key maps". Different device types use different sets of available buttons. Take a look at the Layout sheet in KM and you'll see the different maps by device type.