Why emphasise the EBT when anyone who has achieved Arhathood can teach from direct experience? 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?
Without psychic powers, it's actually quite difficult to determine who is an arahant. Fortunately, the Buddha gave some guidelines in MN47 about how to assess a potential teacher:

MN47:4.1: “Mendicants, a mendicant who is an inquirer, unable to comprehend another’s mind, should scrutinize the Realized One for two things—things that can be seen and heard:
MN47:4.2: ‘Can anything corrupt be seen or heard in the Realized One or not?’ etc...

However, it's much easier to verify the validity of the Early Buddhist Texts (EBTs). Many scholars have compared these ancient scriptures as they were translated and written down in many different countries. The EBTs are remarkably consistent in doctrine. Having faith in the EBTs doesn't require psychic powers.
This principle of faith based on inquiry and evidence is fundamental in Buddhism:

MN47:16.1: When someone’s faith is settled, rooted, and planted in the Realized One in this manner, with these words and phrases, it’s said to be grounded faith that’s based on evidence.

Arahants do teach. Sariputta taught, as did Moggallāna. They had different styles. Sariputta was more into textual analysis and Moggallāna more into psychic powers. And both of their teachings were rooted in the Buddha's own teachings. However, without a Buddha to verify their arahantship, we need to rely on the methods of MN47 to establish a trust in contemporary teachers.
Lastly, the EBTs are continuously translated into contemporary languages and are therefore just as relevant today as 2500 years ago.  Samsara goes on as it does while the wisdom in the EBTs remains directly relevant to this day and beyond.