Mahavakya understanding requires no new experience

 The understanding of mahavakya requires no new experience at all

Tat pada vachyartha: All that is here (known + unknown) is effect, it does not require any new experience as new experiences are included under 'unknown'. Maya shakti of brahman is cause, again maya here need not be experienced, rather is known as existent and as the cause from shastra pramana.

Tvam pada vachyartha: Ones own body mind ego require no introduction or new experience. One experiences the 3 bodies (shariras), requires no new experience. The experiencer I is also not required to be experienced. 

Tat and Tvam pada lakshyartha: The sakshi chaitanyam, which is the knower of all 3 states of waking dreaming and sleep, the reality of the sleeper, the self evident I, requires no new experience, being self evident. Same way the satchitananta consciousness, the reality of the owner of maya who is sat, chit, ananta or limitless is known to be brahman, by shastra pramana.

Asi: The asi refers to the equivalence. Here we apply the bhaga tyaga lakshana to equate the two.  The lakshyartha I, the pratyagatman, is the satchitananda brahman. This again requires no experience, as shastra in itself is the pramana, experience is not a pramana here to establish this bhaga tyaga lakshana, and the understanding of satyam mithya.

Hence without any new experience or any experience to validate , the mahavakya and veda pramana in itself is enough to remove ignorance of self as brahman.

Thus shastra is a pramana for knowing self as brahman satchitananda.