This question concerns some Theravada-based practices, with which I am not familiar.
It is not a dig but a genuine query that puzzles me. Yet I'm not sure that I have asked this question well. I have strong respect for the Theravada tradition.
I recognise the distinctions between a Buddha and an Arahant, (such as the former not having had a teacher, the paramitas, etc.) but these distinctions don't seem to be valid criteria for differentiating the teachings of a Buddha from the teachings of an Arahant, especially in the modern world. Buddha being able to teach in accordance with his audience isn't really relevant to us nowadays - all of his audience died over 2,300 years ago.
Even within the EBT (as I understand it), the Early Buddhist Texts, Buddha repeatedly de-emphasises the importance of himself, and instead emphasises the importance of the Dharma - which is to also to be understood experientially.
Once we have tasted liberation, and we have a direct experience of it - such that every experience we have demonstrates the deep underlying truth of the four noble truths and the paṭiccasamuppāda, why then would we need to teach from a selection of texts from 2,500 years ago?
Again, why is it that the discourses of Buddha, (and some select disciples of his) are 'sutta' but the teachings of any Arahant who has lived in the last few centuries are not 'sutta'? After all, surely it’s the quality of liberated mind that determines the ability to author truth - and certainly not the personality, right?