I think it's a pretty sane model to make the mainline version of a project only handle a small number of architectures, and force people who use rare architectures to create a «portable version». This means the maintainer doesn't have to be an expert on 20 different wonky architectures, and cleanly separates the responsibility of portability from the responsibility of development. This is what e.g. the OpenSSH people do.
As to dropping good patches and then reimplementing them himself while taking full credit, I had not heard such accusations before. Do you have any specific patch set in mind, something to validate this?