Why different CID is created from MFT API and add API?

I have running js-ipfs on browser. I have a question of generated CID by IPFS API.

When I add file by The Regular API(ipfs.add). eg. bitcoin.pdf. I get CID “QmRA3NWM82ZGynMbYzAgYTSXCVM14Wx1RZ8fKP42G6gjgj”

But, when I use MFS( ipfs.files.write).
I get different CID “QmNpjZFnsf6uty2zuEpKCn4YXgZuz1UJhNMTFu4iTLVahM”.

Code is below.

// MFS
await ipfs.files.write('/bitcoin.pdf', this.file, { create: true });
const status = await ipfs.files.stat('/bitcoin.pdf');
// add API
const status = await ipfs.add(this.file);

I think that the path setting has an effect.

But how to get same CID by MFS api?