Not quite true. This is from elsewhere on your link http://ec.europa.eu/social/main.jsp?catId=460&langId=en
People who are employed in another EU country are entitled to live there. Jobseekers are also allowed to stay in another country while they are looking for a job. (See the right to look for a job)
The host country may require them, as "EU migrant workers", to register with the authorities as residents. (See Directive 2004/38/EC)
Other legal and administrative formalities depend on the length of stay – up to 3 months, more than 3 months, or permanent.