Why I can't have similar indices(index) in different mongodb collections?

Question

I'm using nest js for some project I'm working on and I've decided to use Typeorm. I know it's probably better to directly use Mongoose for this but I'd like to have the option to easily migrate to Postgress or MySQL in the future.

From my understanding of MongoDB, I can only have a unique index in each collection, but I can have indices with the same name in different collections, same database. Please correct me if I'm wrong.

I have two entities Foo and Bar

@Entity()
export class Foo {
  // Other columns

  @Column()
  @Index({ unique: true })
  email: string;

  // Other columns
}

@Entity()
export class Bar {
  // Other columns

  @Column()
  @Index({ unique: true })
  email: string;

  // Other columns
}

In my typeorm config, I have enabled synchronization since I'm in development mode. I expect the two Entities/Collections to be created without failing but when I start my application I get the error

MongoError: Index with name: [INDEX_NAME] already exists with a different name

Upon examining the Database using MongoDB Compass, I found that the mentioned [INDEX_NAME] is the email index for Foo entity.

Is there something I'm missing because I can't quite wrap my head around it?