It isn’t an interval, though, it is lifetime. I’m apparently continually failing to make that point.
120k is only the warranty period on the drivetrain/battery, and I’m using it as an example, for parts that have zero maintenance, and are guaranteed for an amount of miles most people never even put on an ICE vehicle that otherwise requires oil changes every 3k-5k miles.
put back the old fluid
Irrelevant. Even being in the position of having a drive unit serviced at all is outside the norm or intent for lifetime of the vehicle.
At a point where a drive unit has to be rebuilt, it’s going to be hundreds of thousands more miles than an ICE would have on it when it requires a rebuild, and engine rebuild means “lifetime” is over. It’s effectively a new engine after that.