C#/ .NET - 为什么string []可以转换为object []但是int []不是？

Question

var isTrue = new string[0] is object[];
var isFalse = new int[0] is object[];

我知道值类型和引用类型之间的区别,但为什么这种行为有意义？特别是从:

var isTrue = "3" is object;
var isAlsoTrue = 3 is object;