There are two elements here, vedas and varnas. Tantras choose vedas to be the principal and not varnas. Thus we often come across a qualitative approach to definition of a Brahmin. For instance,
In Sarvollāsatantram (Matrikabedh tantra) 23rd Ullhasa,
वेदमाता जपेनैव ब्राह्मणो नहि शैलजे ।
ब्रह्मज्ञानं यदा देवि तदा ब्राह्मण उच्यते॥
Only reciting the vedic Gayatri doesn't make him Brahmin, it's when he gains Brahma-Gyaan.
Also, tantras allow vedic practice. See this . Maybe, the thing about real shruti is having this Brahma-Gyaan. For instance,
Gyaan-Sankuli Tantra says,
न वेदं वेदमित्याहु वेंदेदा ब्रह्म सनातनम् ।
ब्रह्मविद्यारतो यस्तु स विप्प्रो वेदपारग: ॥
A sculpture is not merely called veda, the Eternal Brahma himself is veda. The one who spends his time in vedic knowledge and wishes for Brahma-Gyaan is vedic Scholar.
In the other answer as well, it's not 'shruti' which is making a Chandala excel Brahmana but the quality or intelligence of 'Kulin',
In the Mahanirvana Tantra, Chapter 4, verse 42:
श्वपचोऽपि कुलज्ञानी ब्राह्मणादतिरिच्यते ।
कुलाचारविहीनस्तु ब्राह्मणः श्वपचाधमः ॥ ४२ ॥
A Chandala versed in the knowledge of Kaulika doctrine excels a Brahmana, and a Brahmana who is wanting in such knowledge is beneath even a Chandala.
Tantras say this to everyone who are Pashu. For instance,
From the Sarvollāsatantram, 18th Ullhasa,
एते च पशवः प्रोक्ताश्चान्याचारं न जायते।
अन्याचारकृतो येन तद्वदामि प्रियम्बदे ॥ ३४ ॥
वैदिकात् तान्त्रिकात् भ्रष्टो नरके पच्यते ध्रुवम् ।
अथवा पानभ्रष्टो य: स॒ एव पशुलक्षण:।
एतेषां ज्ञानमात्रेण कौलिकस्य क्रियाक्षय: ॥ ३५ ॥
These are called Pashus, they dont have any Achara (ethics/conduct). O devi, Listen to what happens to other Acharas, they get depraved and deviate from Vedic and tantric karmas, and dig there paths towards Naraka. Thus the Pashu-Lakshanm. Remembering these, the Kaulik's kriya becomes useless.
कुमारीतन्त्र-कुलकर्म प्रसड्गस्तु पशूनां पुरतः शिवे ।
कदाचिन्नैव कर्त्तव्यः शूद्रस्य वेद पाठवत् ॥ ३७ ॥
kumari-tantra- Never perform the Kaulik rituals in front of a pashu, its equivalent to a Shudra performing Vedic rituals.