Resolved! DS12288 Rev 4 - Typo in Table 12, page 67
In the first row - corresponds to "Pin Number" D2 for WLCSP81, Alternate functions column, it has:TIM3_CH4,RTIM1_CHE2It should be:TIM3_CH4,HRTIM1_CHE2I emphasized the "H" to make it clear that it is missing. I think this is the only place I saw this.