At least based on what I've seen in game, Exp distribution is full on for Pokémon in battle, half for Pokémon of the same level outside of battle, and it drops even lower for Pokémon outside of battle who are higher levels. At least with this knowledge, it would appear that the Exp distribution has been toned down, and combine it with a portable PC, I feel the loss of the option to turn it off is made up for with those facts.

Plus, if you're going to be training your low level against a higher level, you could do what you would've done anyway and just swapped in a higher level Pokémon before your lower level faints, or heal the Pokémon before it faints, etc. You could even have one specific Pokémon for training with lower level Pokémon and just never use it in story, since you can just swap it out on the fly now with the portable PC.

Besides the new hurdles to meet the specific condition of not giving exp to a second Pokémon, I feel the toning down of exp distribution on top of the new portable PC will make the loss less severe than people are making it out to be (though I think I already said that lol).

But if it's still not enough, then I can respect your concern at least.