But when you stick in cards like this that's a moot point. If you have a 233Mhz PPC with a graphics card and a sound card you've not only replaced the Amiga main CPU to an extent but the custom chips are replaced by non-Amiga parts and most likely PC hardware parts.
Replaced is the wrong word, the custom chipset is still present and usable, you've simply added more capabilities to the system. Now you can run the old classic Amiga software and newer software that takes advantage of additional hardware.
An expanded Amiga isn't exactly an Amiga anymore. It just becomes a dongle to foreign hardware.
Complete nonsense. An expanded Amiga is an expanded Amiga, capable of classic Amiga usage and beyond.