There are many people who think that the gradations among ज्ञानिन्-s, knowers of truth, is made by those Acharyas who came much later after Bhagavatpadacharya; however, they seem to have ignored that Bhagavatpada himself uses the word मन्दज्ञानी in काठकभाषम् !
The orthodox tradition accepts such differences which others reject, perhaps due to misunderstanding gradations in knowers to mean gradations in knowledge! It is very clear that knowledge about one non-dual वस्तु is singular self-knowledge. All other differences in knowers of truth has to do with the निष्ठा, as to how much one can remain in the understanding of the self versus the level of absorption that is disturbed due to circumstances, be it when amidst crowds or left alone, both driven by प्रारब्ध so: the more the वासनs, safely called संस्कारs by some, more is the drifting out of abidance in the self.
Further, Vidyaranyacharya provides a great guide to the categories of knowers in his excellent work Jivanmuktiviveka (JMV), so much so that he explains these gradations well, based on differentiating Videhamukti from जीवन्मुक्ति। There also seems to be confusion among many that lack of जीवन्मुक्ति means lack of मुक्ति, meaning विदेहमुक्ति, itself and that is not the case as is clear in JMV. The clarity of knowledge that guarantees freedom from cycle of birth and death does not guarantee firmness in abidance, thereby making scarce the स्वरूपानन्द which reflects in the चित्त as सुखाकारवृत्ति। The traditional means to deal with such scarcity owing to obstacles is explained in JMV.
ॐ तत् सत्।