Who cares what other people do or how they label things ? but I could see how someone might distinguish them.
Is the purpose for your question to clarify your position in your relationship ? I would guess someone who said "we are dating exclusively" are trying to leave a backdoor for themselves but still keep you tied up just for the mean time till they know for sure about you. Dating exclusively means you go out on dates with only one person at a time, presumably for as long as it takes to figure out whether or not you can stand the person enough to be in a relationship.
Boyfriend/Girlfriend I think it when you know there is more there than just dating.
You know there is some sort of relationship forming and there are true feelings and emotions involved. If there is romantic interest along with sexual chemistry than that is what you call a boyfriend/girlfriend.
If you are spending time and energy with them, but have no interest in them being any sort of a mate, then they are just called "friend." In fact, I suggested to my sons, that they could help ME avoid confusion when they talk about their female acquaintances, if they would use "girlfriend" to indicate romantic interest of some sort, and use "friendgirl" to indicate that the gal is literally just a friend. since many people do have more than one boyfriend or girlfriend, the term "dating exclusively" means something entirely different.
It was established early on that neither of us date multiple people at the same time and that we will be/are exclusive.
As I said, a distinction is made occasionally when we talk. Talk to your boyfriend to get things squared away!!!
Exclusivity = boyfriend/girlfriend Some people will try to twist and squirm obnoxiously that there is a "difference", but reality is that is not the case. No one realistically does that, but people often talk about if they want to become girlfriend/boyfriend. I myself see the labels of "dating exclusively," and "boyfriend/girl friend" to be referencing two almost entirely separate things.
I have known tons of people, including right here in these very forums, who have talked about having more than one boyfriend or girlfriend.