The actual issue is not with 6PPD itself, but when it oxidises to quinones. That transformation was only recognised in 2020, which is why people are only starting to measure and quantify its effects.
It's definitely an issue with ICE and EVs, but is often brought up in EV discussions as people get the impression that EVs are "pollution free" due to their lack of exhaust emissions. Also, EVs tend to produce more tyre dust due to their slightly heavier weight and increased torque.
Incidentally, a small Chinese study found 6PPD and 6PPDQ in human urine in low concentrations. We don't currently know what health effects, if any that may have.