I think you're both right - yes, the harder-steel-in-the-middle is what gets called 'san mai' (though smiths all over the world have forge-welded harder steel to softer iron for tools and in knives for a long time), and the parent was describing a knife with decorative 'damascus' patterns on the outer layers of a harder steel center. I have a similar Shun [1] I got from Williams-Sonoma years ago, which slices onions as usual, but looks good doing it.

1: https://shun.kaiusa.com/