Just read through article and it directly addresses this.
The reason the criteria are relaxed is because of higher hardware specs for the Machine and the fact that the Deck has a small screen. Basically, the Deck has more physical constraints. As the Deck ages, less games will remain compatible.
theorangeninja@sopuli.xyz 4 days ago
I read a comment somewhere that the full controller support and the readability of the text on a small 720p screen, which are necessary for a Steam Deck Verified badge, are not necessary for the Steam Machine. Because it is more like a traditional PC this makes sense imo.