It sounds like there are many descriptive terms, similes and metaphors use to point at Nibbana like fingers pointing at the moon. However, it seems like all of them in isolation and perhaps even all of them together ultimately fall short of completely capturing Nibbana just as a finger pointing to the moon can’t actually touch or hold it.
That said, Bikkhu Bodhi squarely addressed the question of whether Nibbana is simply the extinguishment of defilements or more. Not sure I agree with all of his interpretations, but it appears that he’s citing the EBTs in this section of his essay on nibbana. I wish there were citations in the essay to the EBTs, but here’s the text from the relevant section.
"Nibbana is an existing reality
Regarding the nature of Nibbana, the question is often asked: Does Nibbana signify only extinction of the defilements and liberation from samsara or does it signify some reality existing in itself? Nibbana is not only the destruction of defilements and the end of samsara but a reality transcendent to the entire world of mundane experience, a reality transcendent to all the realms of phenomenal existence.
The Buddha refers to Nibbana as a ‘dhamma’. For example, he says “of all dhammas,
conditioned or unconditioned, the most excellent dhamma, the supreme dhamma is, Nibbana”. ‘Dhamma’ signifies actual realities, the existing realities as opposed to
conceptual things. Dhammas are of two types, conditioned and unconditioned. A
conditioned dhamma is an actuality which has come into being through causes or
conditions, something which arises through the workings of various conditions. The
conditioned dhammas are the five aggregates: material form, feeling, perception, mental formations and consciousness. The conditioned dhammas do not remain static. They go through a ceaseless process of becoming. They arise, undergo transformation and fall away due to its conditionality.
However, the unconditioned dhamma is not produced by causes and conditions. It has the opposite characteristics from the conditioned: it has no arising, no falling away and it undergoes no transformation. Nevertheless, it is an actuality, and the Buddha refers to Nibbana as an unconditioned Dhamma…
The section goes on to reference other EBTs that suggest that Nibbana is more than the ending of defilements only. For example, Bhikkhu Bodhi references the following terms used in the EBTs to describe Nibbana: Ayatana, which means realm or sphere; dhatu, which means element as in deathless element; and pada, which means state as in deathless state.
Bikkhu Bodhi’s assertions can probably be critiqued as virtually any assertion can be. However, these EBT references seem to show that Nibbana cannot be summed up, contained, or fully described in a simple statement like Nibbana is just the ending of the defilements. Seems like we all can agree Nibbana includes the ending of defilements. However, the question remains is that all Nibbana is?
Fortunately, the Buddha gave us many pointers directing us toward Nibbana. However, most of us can probably agree that this question can only be fully answered upon experiencing Nibbana. This conclusion seems strong given the Buddha’s teachings that the truth is subtle, difficult to understand and beyond the scope of reason.