Is there a way to force Qualtrics to use the Accordion Format for Matrix questions? Perhaps with JavaScript? According to the documentation, it seems to be up to the device and the device is not good at knowing when to use it.
Matrix Table
The Matrix Table question type has three viewable formats for mobile devices: Accordion, Normal, and Scrollable.
ACCORDION FORMAT
The Accordion Format for Matrix Tables is turned on by enabling the Mobile Friendly setting in the question Editing Pane. When this box is checked, the Matrix Table will display in the Accordion Format on mobile devices if the table is too large to fit on the screen. If the table is small, the question will display in Normal Format.
We recommend enabling the Mobile Friendly setting for all Matrix Table questions.
If you make the left label column wide enough, it will force it to accordian on all screen sizes.