I mean, I give at least 50/50 odds that what we learn if we lose with the Good Clean Fight (and what our dad and/or Hallr tell us is the lesson is) is that we should've used all our advantages rather than holding back. Like, it's actually bad training to fight differently than you would in a real fight. It's believable because he's, y'know, our brother, but it honestly makes it much worse training for both of them.
Like, in real life you sometimes have to hold back to avoid injury, but holding back any more than that actively makes the training worse, and that's what we're doing here: Holding back way more than necessary.
There's an argument that this is just a friendly spar and so we shouldn't take it seriously, and that argument is fair enough, but it's much worse for learning how to actually fight if we're pulling our punches so I don't buy any argument involving it being better for training. Better for our relationship with Eric? Very possible. Better training? Not a chance.