As Ales has explained, the purpose of using the Find A Grave template is so that the Source citation now has a direct link to the Find A Grave page, which the citation from their page does not do. It is recommended to copy the 'source citation' from the Find A Grave page, then remove the www.findagrave.com url at the beginning of that citation since that is a generic url, then either change the Memorial ID area in the citation to use the Template or add the template at the beginning or end of the citation.
As Ales had stated, the purpose of the template is so that if the url is changed at Find a Grave site, as happened recently, the template will be changed and it will continue to work on all profiles, instead of all the profiles in wikitree needing to be changed.
The full citation from Find A Grave is much more beneficial, similar to retrieving the entire citation from Family Search, instead of just a url, because it will have the date it was accessed, the cemetery name, location, if they exist on the page, as well as the name, birth and death dates found on the page at the time that the citation was retrieved.