Dynamic volume controls were introduced with release of iPadOS 15.4 onwards. For reasons known only to Apple, the ability to either enable or disable this feature is not available for the iPad Air5 and iPad mini6.
Reports suggest that newer models of iPad, that have launched to market after release of iPadOS 15.4, are similarly unable to disable the dynamic controls. These new models are the 2022 11” and 12.9” iPads Pro and the iPad10. At this time, it is feasible to presume that dynamic controls are similarly a standard element of the physical UI of these new models.
Apple have not updated their documentation to indicate that the 2022 iPads Pro and/or iPad10 are similar in implementation within the iPad Air5 and mini6. Hopefully Apple’s documentation will provide needed clarity in due course.
Use the Home, side, and other buttons on your iPad - Apple Support