Yes they do. Apart from the fact that verbalising finalised answers through a third party is a different skill, it takes longer than the 'standard' time for a scribe to listen and note down your final answer accurately, especially in subjects expecting a lot of writing.
Scribes need to read answers back to clarify they have a final version the candidate is happy with and that involves taking amendments from the candidates as they go. It's a long and involved process.
My DH is significantly dyslexic and in the 90s exam boards put down on your certificate whether you had alternative assessment arrangements or not. He was advised not to use any adaptations as employers would view it negatively and had to struggle through his exams unsupported knowing that his work on the few sheets of paper in front of him did not fully reflect what he really could do in a subject.
Being given extra time is also no guarantee that you used it. For some candidates (depending on their support needs) it can provide reassurance that allows them to perform at their best within the standard time.
*Edited to add: It appears the original quote was edited while I was writing my answer.