I hate to say it, but if it took place, I have to think that it constitutes a liturgical abuse. The OF and EF missals are not meant to be “mashed up” in this way — it would be “forcing a round peg into a square hole”. The 1962 missal, AFAIK, does not allow for any variations taken from outside the missal. EP2 didn’t even exist in 1962.
The way the narrative reads here, it sounds like he did a kind of verbal “cut and paste”, i.e., used the EF 1962 missal but inserted EP2, in Latin, where the Roman Canon would otherwise be used.
Archbishop Lefebvre devoted his life to opposing the Novus Ordo and preserving the TLM. It is very difficult to comprehend his making an exception such as this, solely to save a few minutes of time celebrating mass. That’s why I’m skeptical of the story.