XP2 test model, as well as many flatbed style models, is a good test model for hard, brittle model resin but is not accurate for flexible/tough resins like many of our resins (Fast, Blu, Tenacious, ect.) and other brand's engineering resins.
The core problem is that it is too easy to print, and thus:
1) exposure may not pass for accurate work testing as the flatbed does not represent anything the user would print for real work
2) the flatbed is too close to the bottom layers, leading to lights reflecting off and the blooming effect.
3) the model is not easy to distinguish, and users tend to pick too much exposure time as they try to aim for resolution on the model instead of considering other factors
To remedy this, we even created our own and go into detail on how to best calibrate here: Siraya Tech test model V5.