Torah Temimah cites Kerisos.
“From all the commandments” — if there were two pieces before him, one of chelev and one of permitted fat, and he ate one and does not know which — he is liable.
Diyuk of “achat mi-kol” — one from among a defined pair.
Asham talui requires a defined pair of possibilities, not an inherently doubtful single object. When two pieces stand before a person — one forbidden, one permitted — and he eats one without knowing which, the liability is generated. A solitary piece of uncertain status does not trigger the same obligation.