Why can't I load a ModelEntity from RealityKitContentBundle?

If I place the .usdz file in the project directory alongside other .swift files, ModelEntity loads it perfectly. However, if I try to load the same file from Reality Composer Pro under RealityKitContent.rkassets, I get the error: resourceNotFound("heart").

Could someone help me with this? Thank you so much

Code:

//
//  TestttttttApp.swift
//  Testtttttt
//
//  Created by Zhendong Chen on 2/17/25.
//

import SwiftUI

@main
struct TestttttttApp: App {


    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .windowStyle(.volumetric)
    }
}

//
//  ContentView.swift
//  Testtttttt
//
//  Created by Zhendong Chen on 2/17/25.
//

import SwiftUI
import RealityKit
import RealityKitContent

struct ContentView: View {

    @State private var enlarge = false

    var body: some View {
        RealityView { content in
            
            do {
                // MARK: Work
                let scene = try await ModelEntity(named: "heart")
                content.add(scene)
                    
                
                // MARK: Doesn't work
//                let scene = try await ModelEntity(named: "heart", in: realityKitContentBundle)
//                content.add(scene)
                
            } catch {
                print(error)
            }
        }
    }
}

#Preview(windowStyle: .volumetric) {
    ContentView()
}