Can diplomat mean a person with a diploma?

From the site of the American Society for the Prevention of Cruelty to Animals the title "Dip ACVB" is used. As the information I was reading was about certification or qualification, I assumed the "Dip" stood for "Diploma", however the following quote shows that it stands for "Diplomat":

To become a Diplomat of the American College of Veterinary Behaviorists (Dip ACVB), veterinarians must complete a residency in behavior and pass a qualifying examination.
Link

I wasn't expecting that. My next thought was that "diplomat" can mean something like "a person holding a diploma", then in that sense the person with the title "Diplomat of the American College of Veterinary Behaviorists" makes sense because a person can hold a diploma from that college. But I've checked every free dictionary online, and only two related definitions are shown usually. The first one being roughly "a person representing a country". The second one, if given, is usually along the lines of:

2. a tactful person skilled in managing delicate situations.
   Random House Kernerman Webster's College Dictionary

I doubt that the "diplomat" in the abovementioned title means the definition I've just quoted, or any of the others I've found. In any case I could possibly find out what the college means by asking elsewhere.

But my question relevant to this site is can or does "diplomat" mean a person holding a diploma, or was it used in this way in the past? The dictionaries I've checked don't give any such definition.

Edit: As Lawrence has pointed out, dictionaries DO define "diplomate" as a "person holding a diploma".
In that case it may be just a spelling error. Note, I think this word is mainly used in the US, though Google NGrams shows double the frequency of it in AmE when compared to BrE.

Merriam-Webster
Oxford Dictionaries (lexico.com)
American Heritage Dictionary

Solution 1:

In a manner of speaking, yes, a diplomat is a person with a diploma, but not in the way your ACVB quote suggests.

Consider the wikipedia note on terminology:

"Diplomat" is derived from the Greek διπλωμάτης (diplōmátēs), the holder of a diploma, referring to diplomats' documents of accreditation from their sovereign.

Etymonline draws the etymology of diplomat through French and Latin, sidestepping the term diploma:

"one skilled in diplomacy," 1813, from French diplomate, a back-formation from diplomatique "pertaining to diplomatics," from Modern Latin diplomaticus (see diplomatic) on model of aristocrate from aristocratique.

Etymonline's entry for diplomatic suggests a link to the official papers carried by travellers "to the provinces". It notes that the Latin stem diploma refers to "a state letter of recommendation". This is repeated in Etymonline's entry for diploma.

So it would appear that diploma can refer to a document that diplomats (used to) carry; in this sense, a diplomat 'is' the "person with a diploma". As far as I am aware, diploma is no longer used this way. The relevant document is called a letter of credence or diplomatic credentials.

A letter of credence (French: Lettre de créance) is a formal diplomatic letter that appoints a diplomat as ambassador to another sovereign state. Commonly known as diplomatic credentials, the letter is addressed from one head of state to another, asking him to give credence (French: créance) to whatever the ambassador may say on his country's behalf. The letter is presented personally by the ambassador to the receiving head of state in a formal ceremony, marking the beginning of the ambassadorship. - wikipedia

The similar-sounding term for a person holding a diploma from an educational institution is diplomate.

diplomate noun (US) A person who holds a diploma, especially a doctor certified as a specialist by a board of examiners. - lexico

Solution 2:

No - "Graduate" would be the correct term.

My suspicion is the person that wrote that is not a graduate!

The Cambridge Dictionary (and most others)states:

"Diplomat - an official whose job is to represent one country in another, and who usually works in an embassy.", or possibly

"a person who is skilled at dealing with difficult situations in a way that does not offend people."

Nowhere can I find, or have I ever heard of the use of "Diplomat" in the terms used by the ACVB. Perhaps they meant to use "Ambassador" and have conflated this to become "Diplomat".

No question that a Country's Ambassador is also a Diplomat and that (s)he is an official whose job is to represent one country in another and is someone who usually works in an embassy" but, as far as I am aware, the use of Diplomat to identify someone that has a Diploma is (As far as I am aware) an incorrect use of the word Diplomat.

If your aim is clarity rather than 'trend setting' I think I would avoid this usage since, as the questioner demonstrates, it causes confusion rather than clarity.