Is Metamask sending private txn (skipping mempool) on Ethereum chain?

I recently used MetaMask on ethereum mainnet to simply transfer eth. I see to my surprise that the transaction gets submitted as a private txn skipping mempool (similar to going via flashbot). How is it possible- is it that something about the infura RPC has changed?

RPC url: “mainnet .infura .io” (writing with spaces, else MetaMask wont let me post)
How I know its private txn?
*I see going on etherscan that “confirmed within n secs” info is missing in the Timestamp field *

Hi where did you see private tx, could you share more how you made the tx did you use any dapps?