Why does Spring's RestTemplate has setters when Spring also provides RestTemplateBuilder class to build RestTemplate

The following are the methods:

1. public void setMessageConverters(List> messageConverters)
2. public void setErrorHandler(ResponseErrorHandler errorHandler)
3. public void setDefaultUriVariables(Map uriVars)
4. public void setUriTemplateHandler(UriTemplateHandler handler)

I was expecting that RestTemplate would be immutable.

Does it mean that we are not meant to reuse a singleton bean of RestTemplate?

Thanks in advance