I don't buy the whole "if you hear it you'll see it" thing for coding - unless you're used to saying things you're working on I guess, but I'm not. I can see the extra focus it could bring because you're spending more effort in vocalizing your thoughts and it's going trough different systems as well (physically hearing yourself speak).

I've tried both and you can talk yourself trough the problem inside of your head step by step just as effectively when it comes to coding tasks IMO.

Immediate problem solving/planning like "OK I need to do this then this" is a different story - saying stuff out loud helps here.