Mahasi Sayadaw's approach and vagueness in the Tipitaka suttas

Mahasi Sayadaw's approach isn't valid because it attempts to fill in the gaps with commentary from monastics that are supposed to be highly attained? Are there no gaps or vagueness in the Buddha's Tipitaka teachings? If there are gaps or vagueness withing the Buddha's Tipitaka scriptures, can an attempt to fill the gaps in the Buddha's teaching ever be done mindfully, with humility and respect? Also, if a spiritual teaching has gaps or is vague, can there be some kind of a good reason for it being that way?