I didn't follow the TG scene closely back in the day so I'm not sure how widely known some of the lore is within the community, so apologies in advance if I'm repeating stuff --
In reference to the Frampton discussion, there were two interviews (one with the Miami Herald, the other with Videogiochi) that Mitchell gave in early 1984 following a Coronation Day event in Ottumwa. In both, he references achieving a 1.2 million point game in Donkey Kong Jr. (albeit one paper made a name mix-up). Given the controversy around Frampton's score, I found this revelation surprising but ultimately we have two players indicating they were scoring 1.2 million games, albeit Frampton's score was accepted onto the TGIS, the implication is that Mitchell's 1.2 million game was at the time of publication a personal best. Additionally, it demonstrates acknowledgement of Frampton's score on the TGIS.
1) "Teen Videogame wizard vies for electronic donors" (The Miami Herald, 13 Jan 1984)
[In reference to travelling to Ottumwa for the Coronation Day tournament]:
"'I [Billy Mitchell] had to go there and set records in front of witnesses so they couldn't be contested,' he said, ticking off his other high marks: 909,000 at Donkey Kong, 1,214,000 at Pac-Man Jr. and 703,000 at Ms. Pac-Man."
We'll circle back to the Pac-Man Jr aka Jr Pac-Man record of 1.2 million.
2) Videogiochi, April 1984 issue. The excerpt below relates to Mitchell:
https://archive.org/details/Videogiochi_N.14/page/n113/mode/2up?q=twin+galaxies"Quali sono i giochi di cui detenete il record mondiale?
Bill - Pac-man e Ms. pac-Man con I punteggi, rispettivamente, di 3 milioni e 300 mila e 874,300; Donkey Kong, con 909,000; Donkey Kong Jr., con un milione e 200 mila; Centipede, con 25 milioni di punti. Il mio record di Donkey Kong Jr ora ? stato battuto ma ho intenzione di riprovarci presto e riconquistare il primato.
[Google translation follows:]
What are the games that you hold the world record for?
Bill - Pac-man and Ms. pac-Man with the scores, respectively, of 3 million and 300 thousand and 874,300; Donkey Kong, with 909,000; Donkey Kong Jr., with one million 200 thousand; Centipede, with 25 million points. My Donkey Kong Jr record has now been broken but I'm going to try again soon and regain the record."
When viewing the two articles together, it appears to me that the 1,214,000 million Pac-Man Jr score was actually a mixed-up reference to his Donkey Kong Jr score.