Well...not really, no.
It is rare for entire copyrights to be sold as a whole. Generally, if a company hold full copyrights to a work, it is because that work was created as work-for-hire on their behalf by people they hired and directed to create that specific work, not because they purchased the entire copyright of the work. This is true even in the case of a unique physical work: even if you sell the actual painting, you aren't selling the copyright to it, or any right but the ownership of the one physical copy, until and unless that is explicitly included in the contract (likewise, though the original manuscripts of the Lord of the Rings are owned by Marquette University, the copyright of the Lord of the Rings very much remain with the Tolkien estate).
Far more common, when a work is created by an individual creator not working for hire, is that individual rights that make up the copyright will be negotiated separately. The right of publishing in one language, the right of publishing in another language, the right to make a theatrical adaptation, the right to make a video game adaptation, the right to make a televisual adaptation, the right to make a cinematic adaptation, etc. Moreover, beneath those rights there remain the most fundamental right of the author: the right to create further works derived from the original (ie, sequels, prequels, midquels, companion series, etc), and the right to modify the original (write a modified second edition, etc). Sales of those rights, particularly in the same. So, it will be really rare that an artist retain no right based on their copyright.
On top of which, those sales are by contracts, and owning the copyright does give the artist some leeway in being able to pressure for certain clauses in the contract (that are becoming increasingly common as artists are increasingly becoming aware of their rights and increasingly in communication with each other, as often happens), that can grant the artist some degree of continued control or benefits from the work: additional pay per copy sold past a certain threshold is one common example, of course, but increasingly prevalent in modern discussion is the right of reversion, that allow the rights being contracted away to revert back to the artist if the publisher or other right holder fail to actually use them. Other clauses may allow the artists to impose certain limitations or forms of control in other ways on the rights being sold.