I don't think he's too good to be beaten either, but I do think it's unlikely. While 6 points isn't much, the difference to me is that in order to get that close to McDavid, Giroux had to have everything go right for him, while McDavid didn't. While I agree that the end of season pace is meaningless, what's important about the PP for McDavid isn't that PP points matter less, it's that everything points to it being an outlier. The Oilers had a good PP the other season and a half with McDavid and he scored at an elite level those years, and they had an unusually low number of PPOs last year. And while it makes sense that McDavid's speed-based game wouldn't translate as well to the PP, he's too skilled in other areas to not still be great at it. I can't think of any forward who's among the best in the game who hasn't excelled on the PP. And while it's possible his ES points would go down, nothing in his underlying numbers suggest he's in for regression. His on-ice shooting percentage at ES in his career has been a consistent 10.5, 10.9, 10.5. He just produced more chances last year. While it's possible he could have an unlucky year at ES, it's unlikely it would coincide with another unlucky year on the PP, which is why it seems likely he would stay on top.
I'm not usually one to bet against the field, but I'm really leaning toward it with McDavid