No.  `Number(this)` invokes `ToNumber`, which is a different function.  `valueOf` invokes `thisNumberValue` which throws TypeError if `this` is not a number.  `ToNumber` silently converts instead.  For example:
```js
> Number(null)
0
> Number.prototype.valueOf.call(null)
TypeError: Number.prototype.valueOf is not generic
> Number("1")
1
> Number.prototype.valueOf.call("1")
TypeError: Number.prototype.valueOf is not generic
```