I was surprised at the logic:

"....This link also contain CLR Triggers but they can also be a DDL trigger that is why they cannot be count under the pur DML triggers category..."

If CLR Triggers can be something else than DML Triggers, it does not mean it is not the valid type for DML Triggers. It just means it is the valid type for other types of triggers too. The question was "How many types for DML Triggers" and it is 3. This is similar of how we have a "priority one" for so many different things and the fact that we have issues of "priority one" , tasks of "priority one", goals of "priority one" etc does not mean that "priority one" is not a valid type for issues for example because it is a valid type for many other categories.