I'm not sure how this is a difficult topic to grasp
Everyone [clients, contractors, engineers with opinions, whatever] understands that people within a company may hold different opinions - that is a natural challenge of any business to manage
However, from the perspective of something leaving the business on company letterhead, that is irrelevant
The business owns the opinion because they employ the person that wrote it - the business cannot walk away from it arbitrarily
Now, sometimes mistakes or significant disagreements happen and a company (i.e. a group of senior people within the company) may try to walk back something that has been said or done
The obvious example being a senior person realising a junior fucked up on site...again, rationally, most people will understand this and try to accommodate it if they can
But if it's too late - say the project has moved on and the mistake cannot be underdone without cost, then the company foots the bill
They cannot blame their junior and say it was the junior's individual opinion...the company owns that opinion.
So, from a practical perspective, an individual's and a company's opinions are the same once transmitted via formal means
Disagreements are to be behind closed doors only