Its an offence, but its not a conviction or had points applied through
I believe that in the "letter of the law" it is "an admission of guilt" to the offence of speeding.
A conviction comes from going to court and having the matter "proved" against you.
If you take the fine and points you are "admitting guilt", all this can be described as is a "different punishment" - the course instead of the fine/points... both require the "admission of guilt" otherwise you will be prosecuted in the courts to obtain the conviction.
My last renewal specifically asked 2 questions ..
1. Have you been convicted etc etc etc
2. Have you attended a speed or drink awareness course
A bit like asking .. "Have you had an accident......."
All based on the mathematical odds of you having another one ......