Dynatrace does categorize user types (Real, Synthetic, Robots) by looking at the user agent string. For analyzing the user agent a third party database: udger.com is used. You can put the user agent of your synthetic tool into their online parser: https://udger.com/resources/online-parser
The synthetic category is just used for our own Dynatrace synthetic. All other Synthetic solution should fall into the Robot category. If this is not the case, you can either reach out directly to udger.com or create a support ticket, so we can take a look and communicate with udger. In any way we will need the user agent and the name of the tool.
Of course best would be to switch to Dynatrace Synthetic as it will than work out of the box and you have a seamless integration with all the cool features 🙂