No one can give anyone a badge of approval with regards to knowledge of absolute. But if in doubt -- suffering should completely cease, the knowledge should be effortlessly present at all times, and also the urge to search for further truth should cease because one knows with utmost certainty that one knows all there is to know with regards to the nature of absolute.

If someone answers "no" to any of these questions, they may have only intellectual understanding of what to look for (which is a very important step on the journey).

As for your question, "But why?" I would say because it describes the Absolute pretty well. However, there are many apt descriptions. Hinduism itself talks about Brahman (very broad term), Satchitananda (existence-consciousness-bliss), but also e.g. reality-knowledge-infinity, supreme self, and many others. Taoism calls the same Absolute simply "Tao that cannot be spoken". Buddhism uses the obscure word "suchness" and ambiguous phrases like "Form is empty; emptiness is form." And then you also have the Abrahamic God whose true name is hidden but the only time he explicitly states it he goes by, "Ehyeh Asher Ehyeh". And all of those terms denote the same. But always keep in mind that they are just the proverbial fingers pointing at the moon.