Not sure I understand. The "open original.." is a plain link with target="_blank", and Minifeed is a pure classic HTML web app with zero JS shenanigans. There is nothing which can manipulate the history.
Since the link opens in a new tab by default (because of target="_blank"), that new tab naturally does not have a "back" history. Is this what you mean?
I wish target="_blank" had never been invented. I'll decide for myself if I want a new tab, thank you very much. I've never found an extension that filters out this garbage properly. There's one appropriately called "Death To _blank", but so much still slips through.
On ios it does not do that. When I click on the original source link it replaces minifeeds page in the current tab. I can the ln click back and it does take me back to minifeed but then I cant click back again to get back “one more” to the minifeed index.