I am exactly the same. I feel like social anxiety has genuinely very little impact on my speech. It definitely does but I stammer almost the same if I’m cuddled in bed or at work with people. I know exactly my ‘safe’ and ‘bad’ letters and I know exactly what kind of sounds and letter combinations make me stutter. I also noticed a weird phenomenon with letters ‘D’ and ‘T’ where my tongue basically goes outside of my mouth instead of the top of my teeth as if it’s paralysed and it can’t produce the sound. To make things funnier I study dental technology so I’m basically done for whenever anyone asks me what do I study/do for work 😀. I’m fortunate to have my name begin with my ‘safe’ letter, however my surname and D.O.B. do not. My current address also doesn’t. So every GP, healthcare or phone appointments always end up the same for me as they need to confirm either your D.O.B. or address or sometimes both cause why not 🙂.