Why string[] is interpreted as object[], not as object, but we can assign object obj = new string[]?

I currently am learning about Reflection late binding from this video.

And as I replicate the code in the video, there was one part which puzzles me. It is when Invoke method is used:

MethodInfo getFullNameMethod = customerType.GetMethod("GetFullName");
string[] parameters = new string[2];
parameters[0] = "First";
parameters[1] = "Last";

//here is where I got confused...
string fullName = (string)getFullNameMethod.Invoke(customerInstance, parameters);

As far as I can see (also shown in the video) Invoke has input parameters of (object, object[]) and has no overloaded method with input parameters (object, object).

What being passed here are (object, string[]). And so, at first I expected that there would be compilation error as I thought string[] is an object rather than object[]. But.... there is no compilation error.

That puzzles me: why string[] is an object[] rather than object (every Type is C# is derived from object after all)? Can we not assign string[] as an object like this?

object obj = new string[3]; //this is OK

How can a string[] is both object and object[]? Using other data type, say int, as an analogy, I will never expect a variable as int and int[] at the same time.

Can somebody enlighten me?

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Here is my full code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Reflection;

namespace ConsoleApplication2 {
    class Program {
        static void Main(string[] args) {
            Assembly executingAssembly = Assembly.GetExecutingAssembly();
            Type customerType = executingAssembly.GetType("ConsoleApplication2.Customer");
            object customerInstance = Activator.CreateInstance(customerType);
            MethodInfo getFullNameMethod = customerType.GetMethod("GetFullName");
            string[] parameters = new string[2];
            parameters[0] = "First";
            parameters[1] = "Last";
            string fullName = (string)getFullNameMethod.Invoke(customerInstance, parameters);
            Console.WriteLine(fullName);
            Console.ReadKey();
        }
    }

    class Customer {
        public string GetFullName(string FirstName, string LastName) {
            return FirstName + " " + LastName;
        }
    }
}