In order for us to consider adding callback support to the 'count' aggregation method in MDL-82464, then we first need to evaluate all current columns of type column::TYPE_INTEGER|TYPE_FLOAT to ensure we don't inadvertently change their behaviour

Per the class documentation the type of the column defines two things:

1. How the value of the first parameter to the callback is cast;
2. The available aggregation options for the column

We have a lot of entity columns with code similar to this, which is using the column type purely to get the first parameter value cast (they often subsequently disable numeric aggregation options, which rather proves the point they do not represent numeric data)