To me, it means the same as You Mileage May Vary. It means not every customer will get the same treatment. I'm not saying this in a negative tone. Actually, it can be quite positive if we can all get over our natural instinct to be cynical with regard to the hobby.
If a provider is sincerely open minded, it means she will consider almost every reasonable request in terms of activities. It also means, she reserves the right not to participate in certain activities. To me it means that if the provider trusts the client and has a connection with the client, then more is probably on the table.
So, how does a client stand a chance at "opening the mind" of a particular provider? For starters, be a gentleman and considerate of your partner. Take nothing for granted. Second, follow all the normal hygiene rules-- showered, clean smelling, clean and neat down there, etc. Finally, act like you know what you are doing. This will disarm any of those lingering doubts and allow the provider to reciprocate.
Then again, maybe it is just a marketing ploy to attract potential fence-sitting clients. Yeah, yeah, the cynic in me just had to make the comment