Potential error for definitions of == and !=

[Mikerah]

While going through the grammar, I noticed that in the definitions for == and !=, we have the following

e10
    : e10 '==' e9
        {
            if (($1.type == "NUMBER") && ($3.type == "NUMBER")) {
                $$ = { type: "NUMBER", value: $1.value.equals($3.value) ? bigInt(1) : bigInt(0) };
            } else {
                $$ = { type: "OP", op: "==", values: [$1, $3] };
            }
            setLines($$, @1, @3);
        }
    | e10 '!=' e9
        {
            if (($1.type == "NUMBER") && ($3.type == "NUMBER")) {
                $$ = { type: "NUMBER", value: $1.value.eq($3.value) ? bigInt(0) : bigInt(1) };
            } else {
                $$ = { type: "OP", op: "!=", values: [$1, $3] };
            }
            setLines($$, @1, @3);
        }

Here, for ==, value is defined with $1.value.equals($3.value) and for !=, value is defined with $1.value.eq($3.value).

Is this is a bison/jison particular thing or a typo?