only sort of true. it's been reported in several places, but the upshot is if the exhaust is not epa compliant the dealer is supposed to void the powertrain portion of the warranty. obviously, if you change pipes and your infotainment craps out, they 'should' cover that.
but you can go aftermarket, as long as it is epa compliant. and with the m8s being so new, not much, if anything, out there. yet.
Harley just had a run-in with the EPA. It has been mandated by the government, as part of the settlement, that for '16 and newer bikes, if any modifications to the powertrain are made, and they're not EPA-compliant, then Harley
must not honor any warranty claims on that powertrain. They cannot warranty such a situation or they will be defaulting on the settlement.
There are never going to be any aftermarket parts (aside from maybe cat-back exhaust - mufflers) that will be EPA-compliant since to become
compliant the whole package has to be certified. The only such packages are Harley stage kits, and they must be used in their entirety to maintain certification status. And this includes the specific ECM calibration.
There's no way an exhaust, or intake, or cam manufacturer is going to spend the time and money to get any kind of certification from the EPA. It's just not feasible.
So unless one uses the complete H-D stage kit, with ECM calibration and all, to modify their powertrain, or unless they do otherwise and can completely cover their tracks, anything that might happen to the engine is going to be on their own dime. The Magnuson–Moss Warranty Act will not be able to come to anyone's aid once there have been non-compliant modifications made to the way the engine produces power. And frankly, that's the way it
should be anyway. If I were making and selling a motorcycle I would not want to warranty the engine "regardless what the purchaser might have done to modify it." I would only feel obliged if they'd left it the way it was when I made it.