In the transcript of these conferences, as also the transcript of the sermon given by Bishop Zendejas last year quoting them which appears on the Dominicans' website (see here: https://www.cathinfo.com/sspx-resistance-news/bishop-zendejas%27-advice-on-1962-liturgy/), the Archbishop is quoted as saying:

I knew the president of the Commission who did this reform, it was Msgr. De Matto, who was the Abbot of St. Paul outside the Walls… I know him very well and I spoke with him many times. He was the president of the Commission of reforming the liturgy under the Pontificate of John XXIII. It was under Paul VI that he was removed because he was traditionalist, and they replaced him by Msgr. Bugnini

For the public record, it appears that "Mgr De Matto is a typographical error and is in fact referring to the Benedictine Bishop, Abbot of St Paul Outside the Walls, by the name of Cesario D'Amato. From what I can ascertain, he joined the Commission in 1960.

See the list of abbots here:
https://en.wikipedia.org/wiki/Basilica_of_Saint_Paul_Outside_the_Walls

See his biography here:
https://it-m-wikipedia-org.translate.goog/wiki/Cesario_D'Amato?_x_tr_sl=it&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc