You win, you are correct in being pedantic, I should not have said 'understood'
ROGER I have received all your last transmission.
Note: Under no circumstances to be used in reply to a question
requiring a direct answer in the affirmative (AFFIRM) or
negative (NEGATIVE).
But it doesn't change the general drift of the topic in terms of the role of an A/G operator and the purpose of calls such as 'ready for departure' at an A/G field, which are certainly not meaningless to pilots.