ChNN frequently says this actually, but he does not mean realization of emptiness free from extremes, he means an experience where the mind is empty of thought.
Like non-thought as in bliss, clarity and non-thought? He actually means something like non-conceptual?
It makes a great deal of sense in these terms, from the perspective of the Pali Suttas, particularly from the second jhaana/dhyaana. According to the Suttas, five factors enter into the first jhaana/dhyaana:
vitakka/vitarka, "thought", applying the attention to the object;
vicaara, reapplying the attention to the object, as it were;
sukha, happiness; and
Vitakka/vitarka and vicaara are terms which refer to the conceptual, though the conceptuality is so highly attenuated in the context of jhaana/dhyaana, on traditional accounts which follow Buddhaghosa's Visuddhimagga at least, as to be more naturally describable as non-conceptual or verging on it. In the second jhaana, vitakka/vitarka and vicaara cease, so even tenuous conceptuality ends, and only piiti/priiti and sukha (which are not distinct from one another at this stage, and which are technically vipaaka -- the result of past kamma/karma), together with ekaggataa/ekaagrataa, intensified by the bliss, remain. In the third jhaana/dhyaana, piiti/priiti falls away, and in the fourth jhaana, sukha also falls away, leaving upekkhaa/upek.shaa (equinimity) in its stead and ekaggataa/ekaagrataa. In the later mainstream account of jhaana/dhyaana given in the Visuddhimagga, and as jhaana/dhyaana is practised and taught by such Theravadin teachers as Pa Auk Sayadaw and Ajahn Brahmavamso, the mind is empty of thought, to all intents and purposes, even in the first jhaana/dhyaana. From the second jhaana/dhyaana upwards, the qualification "to all intents and purposes" is not needed: the mind is empty of thoughts, full-stop.