To start my elaboration of my question, i am aware that the Mandukya Upanishad is traditionally attributed to the Atharva Veda. Nearly everywhere on the Internet, the text is attributed to Atharva Veda. Even the Muktika Upanishad attributes it to the Atharva Veda.
Now, i have a doubt on this attribution for a few reasons as below.
The Sakha of the Mandukya Upanishad is not known (from what best i could find out, pls correct me if i am wrong). The Sakhas of Mundaka and Prashna (other commonly attributed upanishads to the Atharva Veda) are commonly attributed to Shaunaka and Pippladha rishis respectively (and so the sakhas named after them). This data point as acceptable since it goes well in sync with Srimad Bhagavatham Canto 12, chapter 7, verses 1-4 (SB 12.7.1-4)
SB 12.6.54-56 states Mandukeya as a student of Paila, belonging to the school of Rig Veda. The name Mandukeya is not mentioned under the Atharva Veda section SB 12.7.1-4.
The relationship of Mandukeya (manduka's son) with the Rig Veda is further clarified with the mention of this name in the Aitreya Aranyaka 3, Adhyaya 1, Khanda 1.
This Wiki page states MandukAyana as a shaka of Rigveda (from Saunaka's Caraka-vyuha) and also calls our Manduka as a shaka of Rig Veda (from Sri Gurucharitra). All the same sources do not mention of Manduka/Mandukya when discussing Atharva Veda shakas.
All this makes me think - Is Mandukya Upanishad attributed to Rig Veda rather than the Atharva Veda.
So, am i missing something or is this inference right? I request people here to please shed some light on this topic.