I was asked to comment on this thread - and I hope I can add my 2p to the topic.
The verbal root man already has a past passive participle in the form ‘mata’ - and this is also the invariable Sanskrit (both classical and vedic, right from the Ṛgveda, for eg. ṚV1.46.5 ādāro vām matīnāṃ nāsatyā matavacasā) form of the past passive participle of this root.
So to regard muta as a lexical variant of the same mata seems slightly odd (particularly where there is no semantic change discernible) - as mata is also well attested across the tipiṭaka. So perhaps the ‘u’ in muta is pointing to a different root related to thinking but not really = mata?
I think Sanskrit smṛta (from the root smṛ “to remember/recollect”) might have possibly become muta (with the disappearance of the initial ‘s’, the ‘ṛ’ becomes ‘u’ under the influence of the preceding ‘m’, as both m & u are labials). However there is also the usual past passive participle form sata (where it is the m that disappears from smṛta, leaving behind the initial s, and whereupon the ṛ becomes ‘a’ as there is no preceding labial).
So if we take muta/muti as grammatically equivalent forms of sata/sati (both from the root smṛ) then we may possibly tie down ‘sata’ to its unique buddhist sense (sati = mindful?) and ‘muta’ to the generic sense ‘remembered’ – while standard sanskrit only has one form smṛti and smṛta.
So the probable translation of diṭṭha, suta, muta & viññāta = observed, listened, recollected & understood respectively.
I don’t see how muta can mean ‘sensed’ - what would be the verb root in that case & how would that postulated meaning fit the root?