I believe the subvocalizing thing is a myth. As you process the letters faster, you no longer say the letters, if you ever did.
A pianist doesn’t think, That’s a C, use the first finger to hit that key.
As part of trying to drive phonics out of existence, the Education Establishment told a lot of lies.
Have it your way. However, I’m extremely glad that phonics was never forced on me, and I’m extremely happy with the results my own children had when we decided (homeschoolers) that phonics was a poor approach.
It’s not a matter of saying the letters. Sub-vocalization is the process of internally saying the words to yourself, not the letter. Good visual readers do not hear the words when they read.