Is it actually possible to roll miles back on an X5?

[Corellian Corvette]

Strange question but simple reason for asking.

Looking at an X5. It's been modified in very interesting ways (it's a 4.4 but has been turned into a 4.6 clone; 4.6is body kit, 4.6is seats, even heated seats which weren't originally in the car), 4.6is Exhaust.

Normally this is no big deal in fact that's why I'm interested.

Ran a Carfax and it shows a mileage discrepancy. When it moved from CA to Nevada the mileage was listed a 99,087 in 2016, but a year later in Nevada it was listed as 78,334. Subsequent reports went up linearly to current mileage shows 89,233

I've seen a lot one-off mileage issues in Carfax but this one seems stranger. There are no accident reports, no salvage reports. It shows reasonable mileage up to 99K, then suddenly down to 78K and a reasonable trend back up from there.

So that's super weird. The cluster shows no tamper dot.

So I'm of two minds. On one hand, this car has clearly had some modifications although none of them I would consider that unusual. I've swapped seats and bumpers in tons of BMW's. And if you're going to tamper with the mileage, why only take off 20K? Might as well take off 50K and really make it worth doing. To me there is functionally no difference between a car with 90K and a car with 120K.

On the other hand - whoever has done these changes did a good job. They knew enough to swap over parts from a 4.6 including heated seats - and this car has PDC, RDC, and basically every feature so they would have needed a matching cluster with ALL those features AND the heated seat buttons. So somebody smart swapped this stuff. And it's a bit suspect this happened right as the car was going to hit 100K.

So all this brings me to the key question which is, AFAIK, there is no real way to roll back mileage like this. You could get a cluster with lower miles, but you'd have the tamper dot. And I don't think you can code a mileage change in every module.

Maybe I'm wrong and someone will say it can be done, in which case I guess I should assume this had miles rolled back.