Some earlier analyses of the Hungarian case system, such as László Antal's A magyar esetrendszer (1961) did not consider the essive-formal to be a case, and disputed the status of the suffix -ként in the declension system.
However, this is not unique to the essive-formal; -i can follow other case suffixes, for example -ban/-ben in nagybani, though it has become less common since the early 20th century (e.g. ágy(tól) és asztaltóli elválasztás).
Another reason was that most Hungarian case endings participate in vowel harmony, while -ként does not, possibly due to its later development.
However, the essive-formal case complies with the criterion for Hungarian cases set by modern descriptive grammars,[1][2][3][4] namely that it can appear as the argument of a verb, specified in its form, such as in kezel (vmi)ként (’treat, handle as ...’), viselkedik (vmi)ként (’behave as ...’), végez (vmi)ként (’graduate as ...’), elhelyezkedik (vmi)ként (’find employment as ...’) etc.
Therefore, it is today considered as one of the 18 established and acknowledged cases in Hungarian, rather than being one of the adverb-forming suffixes, which do not comply with the criterion.