Hi @tbonkers ,
Thanks for your interest in the NXP MIMXRT product, I would like to provide service for you.
In IMXRT1160RM refence manual chapter 72.3.2.3 Counter Synchronization.
https://www.nxp.com/webapp/Download?colCode=IMXRT1160RM
It describe PWM Counter Synchronization, Please refer to this.

Wish it helps you.
If you still have question about it, please kindly let me know.
Wish you a nice day!
Best Regards
MayLiu