i don't think it's ironic. seamicro has been selling intel based servers as far i know. they won't suddenly stop selling intel servers just because amd recently bought them. to amd's advantage, they can use seamicro to sell their own opteron based servers. i don't think opteron's performance has anything to do with it.
an excerpt from that article.
As it stands, SeaMicro has a tight partnership with Intel, and every SeaMicro server uses Intel chips. According to AMD, SeaMicro will sell Intel-based servers “for the foreseeable future,” but an Opteron-based solution should arrive by the end of the year.
partnerships are not that easy to terminate. there might be high compensation fees involved among other issues.