Admittedly I haven’t used gmail for years now but from what I remember when I used to do this this is half right. If you change the From address in gmail, it will add a ‘Sender:’ header with your gmail account on it. Some clients will show that combination as the email being from ‘X on behalf of Y’ where Y is the from address and X the sender address and some will send replies, especially bounces, to your sender address. It may also set off some spam traps. I think it might also have required some form of verification that you have access to the address in question.

If you want to send from a different address without the sender header being set to your gmail account, I think you have to have Gsuite.