Confidence and skills are two separate things. We all the know someone that talks a big game but doesn’t back it up with successful action. Conversely, we all know someone with incredible skills that doesn’t talk a lot. They rather let the work speak for themselves.
A skilled person is confident by default whether or not they have a big mouth. The unskilled wannabe has to fake it until they can catch up with their glib talk.
The mouth is strategic. Actions are permanent. Faking it is a wise holding strategy that builds confidence but doesn’t necessarily manifest itself in skills. The work is the only thing that really counts.