Track Device Pose with Rotational Tracking does not extended track the ImageTarget

Vuforia SDK Version: 8.3.8 - Description with steps to reproduce: Hi, Im using Unity 2019.1.14f1 and Vuforia 8.3.8. and build for an iPhone 6, 7. When I enable "Track Device Pose" and select "Rotational Tracking" the scene has the same behaviour as when i disable Track Device Pose completely. I expected that the "Rotational Tracking" would be a sort of lower quality extended tracking like the ones from previous vuforia versions. The reason why I want to use the old way of extended tracking is because on iPhone 6 and iPhone 7 devices the "Track Device Pose" with "Positional Tracker" enabled, causes lagging. It seems that this function needs too much performace of these older devices. Could you give me a hint how I can use the old extended tracking using only inertial sensors instead of the VISLAM way ? greetings, - Development OS (Mac OS X, Windows, Linux): Max OS X - Mobile OS and Version: ios 12.4 -