I would say that yes, Paul was a trusted member of staff, yes, Diana relied on him to keep her household running smoothly. But, was he on the same level of importance to her as her closest friends and family? Of course not! And I certainly doubt that she confided her deepest secrets to her butler, however well they got on.
Plus, there is evidence that Diana became irritated by his presuming too much all the time. Burrell may well have been her ex butler by the end of the year had she lived.
With secrets, I respect your position she would not do that with him. Based on accounts from others, I believe she did share personal things with those she was comfortable with in a way that was unconventional...meaning she didn't always observe strict 'boundaries' about her personal life, with insecurities and problems hidden away, bundled and tightly wrapped, as most of us tend to do.
If she was irritated as you mention, we can pursue that.
What strikes me most from Paul is how proud he is of everything he did for Diana, and since he was the one who interacted with her and his experience transcended typical butler, a refusal is there to redefine himself as others
insist he was a butler, and
nothing more than a butler. Can we really blame him for speaking out if the interaction with his employer
went miles past this ?
The link below is one that will cause consternation. To lessen discomfort to others, a short part is highlighted. [ Inviting him to Kensington ] If in fact he's
dead honest about it, I personally do not find it shameful or terrible. I believe he's repeating accurately what was spoken.
https://www.mirror.co.uk/news/uk-news/paul-burrell-reveals-princess-diana-10005442
"We were best friends, like brother and sister, and shared lots of secrets.
"Her reliance on me was so great she even asked me to move into Kensington Palace.
“I told her, ‘Yes, but the problem is Maria and the boys. They need me and I need to be with them, and my family is very, very important to me.’
“‘I understand that, she said, ‘But wouldn’t it just be fun if you lived here with me.’ She often joked about that.
“Diana just thought I could simply walk out and get on with another life. But how could I do that to my family?”
...though the boys have not been in touch iwht him for years, he embarrasingly shows up at Harry's wedding. NOT the signs of a decent or stable man..
Since he went to the wedding with a good heart, and good intentions, then in some ways it speaks of decency.