It's like these two example statements:
I'm going to meet her.
I'm going to meet Jasmine.
Now obviously her could refer to anyone, but a few moments later it's clear that her refers to Jasmine.
The only difference is one was a bit more explicit.
Unless I had a secret affair with Jasmine, or like some episodes of Pokemon I don't know her name prior. I can't really see the difference between the two. Or why one can't be more explicit than the other statement.
So Ash saying he's going meet Pokemon. Compared to "I'm going to meet all the Unova Pokemon." Is just as negligible.
Now let's look at Ash's character overall. Why would he be so picky and say "I only want to meet some Pokemon in the Unova" sounds to me like Ash knows he's going to run into a real nasty Pokemon and doesn't want to meet it. Judging by Ash's character he isn't going to be prejudice/discriminatory like apparently his original statement appears to imply.
Except to Ash wouldn't any Pokemon he's never seen before be "Rare and Unusual" while I admit I guess there's a difference between the two, but again comes off as prejudice/discriminatory.In the original, Okido said he'd be looking forward to hearing about any rare and unusual Pokemon Satoshi met, while in the English dub, he says he's looking forward to hearing about anyone and everyone Ash comes across. That explain the differences better? The line is definitely a rewrite.
Aside from viewer obviousness, what makes Cobalion more rare and unusual then Patrat, when to Ash at first everything is going to be rare and unusual?
Then again why should it matter in the end? As far as we know Ash hasn't even contacted Professor Oak yet.
What he's only going to contact Oak about some giant electric blasting Pokemon like Zekrom. Hell he called Oak about Turtwig evolving, I'm sure Ash would call oak about his captures and adventures, but he hasn't done that yet. Who knows when Oak will reappear in the Best Wishes series.