Hello,
I'm using my own design based on TWR-VF65GS10 for most part, and autoEVB for Ethernet part. In my case PTB8 is used as FTM1 chan0 capture mode. I set IOMUX with 0x00101201, and at the end I get 0x0000219e.
At this moment, I don't have enough time to dig deeper, I will do it in few weeks, as workaround, M4 MQX application rewrite IOMUXC, dirty but it works.
Emmanuel