There is no “actual style” of a shell pipe. A pipe is just a sequence of bytes, it has no style/type associated with it.
pbcopy decides to interpret the stream of bytes that starts with {\rtf1 as RTF and process it before it is stored in the clipboard. But this is not without problems. For example, if you run the command:
echo '{\rtf1 is what RTF files start with' | pbcopy
You get a broken clipboard, not the text that you sent to pbcopy.
So maybe Keyboard Maestro should do the same, or maybe it shouldn't - its not a clear cut case.