You're still not getting it. Here are the facts:
^^^ Comical Irony Alert ^^^
1: You said that a forfeit is always a loss.
A forfeit is a specific type of loss, just as rain is a specific type of precipitation, and a beagle is a specific type of dog.
2: Stalemate isn't a loss.
The logical result of a stalemate is a loss, of the specific type known as "forfeit".
3. Therefore a stalemate can't be a forfeit.
Utterly absurd. Forfeit can certainly be the result of a stalemate, just as a draw can be the result of a stalemate, or a win can be the result of a stalemate, or a generic loss can be the result of a stalemate, all depending on what the rules specify as the result of a stalemate (win, loss, and draw have all been specified by various chess rules throughout history). Logically speaking, the result of a stalemate is forfeit, however.
It's basic logic.
Not even close. Here is an illustration of how absurd your idea of logic is:
Suppose I said that a draw is a specific type of win, i.e., a "lesser win" which is awarded to both players (both players win 1/2 point each). Then you came along and said:
1: You said that a draw is always a lesser win.
2: Stalemate isn't a lesser win.
3. Therefore a stalemate can't be a draw.
This is not a definition of forfeit. This is just a sentence - "fofeit is a situation when player is unable or unwilling to play". It's like saying "A is B". Claiming that from "A is B" follows "B is A" is a well-know logical fallacy. So even if your statement is correct it doesn't mean that every situation when player is unable or unwilling to play is a forfait.
Example 1. Player might be unabe to play because of illness. Game is postponed.
Example 2. In amateur tournaments a player or a team might be unwilling to play on a scheduled day. Game/match is postponed.
Finally absence of legal moves has nohing in common with any other kind of inability to play. It is never called a forfeit in any sport/game and hence doesn't belong to a "forfeit concept".