Oh sure. Obviously there are coins which you could say without argument, are definitely mules, such as that Jersey Penny. As well as the overwhelming majority of coins, which aren't.
The difficulty lies in the grey area in between, and it is that which we will probably never achieve total consensus in.
As far as "intent", for me that would have to be officially sanctioned intent. If a die operative on the day inadvertently married up incompatible reverse and obverse dies, then you could argue that his intent was to use the correct dies, but due to a mistake on his part, an erroneous combination was used. The problem with this, of course, is that in most cases you won't know with absolute certainty whether it was a mistake at the sharp end (as it were), or an agreement deliberately arrived at, in the full knowledge of what dies were being used in combination.
Another area of possible debate would be at what level an intentional decision was made to use incompatible dies. It could be made at operative, or foreman level where the intended die was broken, but to fulfill targets an incorrect one was used. In real life any number of possibilities rest as a potential, and the reasons will have been lost in the mists of time even by the following weeks of production, let alone 150 plus years later.