To be able to use the Cortex-M, the proper device tree overlay should be enabled in TorizonCore.
This is verdin-imx8mp_hmp_overlay.dtbo and, as you can read here it has been added to the iMX8M-Plus builds recently.
TorizonCore 6.2 doesn’t have that device tree, and I suggest you to use the last montly 6.3.0-devel-202305+build.7.container.
Please, do not forget to run the commands suggested here otherwise you won’t be able to boot TorizonCore.
The Cortex-M usage has become a quite popular topics in the last few months. If you search on the community, you can find some useful topics.
Please, refer only to recent topics, and not to old ones, since the HMP support has been increaded a lot in the last few weeks.