Amazon has a habit of making up words and pretending everyone already uses them. Perhaps they think not referring to "earnings" will help disguise they are earning money hand-over-fist?
"Peak" is their latest one, as in "Ensuring everyone is ready for Peak". Apparently "Peak" refers to the holiday shopping season, starting with Black Friday. Nevermind everyone in the industry calls it "the holiday season".
Been in this (online) industry for a long, long time, never once heard of it referred that way. I'd think you'd need to quantify what "peak" you're talking about, as-in "Peak Sales" or something. And, not everyone's "peak" is at the same time, so it's odd to refer to it that way.
It's not an odd word choice, see also https://www.apple.com/newsroom/2020/07/apple-reports-third-q... and many others
https://www.google.com/search?q=%22quarterly+earnings%22 4.5 million results
https://www.google.com/search?q=%22quarterly+results%22 5.5 million results