One person holds the profile, the copy, the exclusions and the replies in their head, and everything stays consistent because it never leaves that head.
Add people and the consistency has to be written down or it disappears. The profile becomes a document. The copy gets an approval step. Personalisation gets checked instead of trusted.
That is real work, and it is the reason growing teams get worse before they get better.
How we do it
We do not scale by adding operators. Volume is bought with more domains and more mailboxes, and the same person keeps the profile, the copy and the replies.