My one minor gripe with this story, and it really is nitpicking, is the abrupt attitude change in Arven from when you first meet him at the lighthouse lab, and when he acts all chummy when he is trying to convince you to help him out with his quest. Even then, there are two built-in possible explanations that don’t stretch the imagination too far. The first potential explanation is in Arven’s dialogue itself. He is in desperate need of someone with powerful Pokémon to help him defeat the Titans, he doesn’t have friends who are strong enough, and he really doesn’t get along with Nemona. And so, with nobody else to turn to, he has no choice but to ask the player for help, despite being aggressive with them earlier. It’s the classic disingenuous “I need a favor, so we’re best buds now” routine. The second possible explanation is a bit more speculative on my part, but it does fit Arven’s character. Arven really does want to be friends, but he isn’t really sure how to approach the player after brushing them off so harshly earlier. As such, he kinda just tries to sweep that under the rug. It would explain why he rushes off before the player can answer on whether or not they want to help find the Herba Mystica. As I said, it would also fit with his socially awkwardness, having basically grown up isolated from other people thanks to being abandoned by his parents.
To be fair, as someone who grew up with Gen 1, I get it. If you blew it on the Legendary birds or Mewtwo, you didn’t get a second chance. But, in general, we knew that those were powerful Pokémon, and that we should save in front of them, to give us as many chances as we needed to catch the field encounters. That said, it has been standard now for several generations for field encounters to respawn after certain tasks have been completed, such as defeating the Elite Four. Also, this was an encounter generally surrounded by other Pokémon, and, while it was programmed to not trigger unless deliberately tripped by the player, the only indication of this was a brief text box with the Pokémon saying its cry. That comes off as unusual, but without any special animation or jingle in the battle that would distinguish it from the thousands of other encounters with that particular species, it comes off more as a weird quirk rather than a signal that this is a particularly special Pokémon. With the games being as buggy as they were when they first came out, it was entirely possible for someone to either not notice that they specifically triggered the battle or to assume it was just a glitch. In my case, it was the latter. I found the Ex-Titan Klawf in Scarlet without realizing that it was a special encounter, and KO’d it. While I'm glad this issue has finally been resolved with the DLC patch making it so the encounters respawn, it's just silly that it took them nine and a half months to fix what should have been a very simple issue. I suppose that’s because they had other, game breaking issues to deal with first.
As the story progressed, everything about Arven, including his initial aggressiveness, his clumsiness when cooking (seriously, the guy is completely self-taught, it’s a wonder he can cook at all), and his personality in general fell into place. Far and away, out of the main “quest trio” of Nemona, Arven, and Penny, I would argue that Arven is the most well developed character, and he has the depth to back it up. Nemona is a fantastic rival, and I would say she’s the best rival in the entire franchise, but, as I previously mentioned, she is fairly one dimensional, and you don’t get to see the depth to her character until after her story arc. Penny meanwhile gets outclassed in her own story arc by Clavell, mostly because she doesn’t really have a presence in the story until the very end. Arven’s struggle, both to make new friends and to save his best friend Mabosstiff, are very touching moments; you genuinely feel happy when Mabosstiff fully recovers after eating the final sandwich. The conclusion of this arc, which directly ties into the next part of the story, also sets up the relationship between Arven and his famous parent extremely well, which is good, because that particular dynamic comes to the forefront during The Way Home. Up until that point, the game had pretty much been entirely expositional about Arven’s relationship with his parent. Now, we actually see that particular dynamic playing out, when the Professor calls the player to congratulate them on getting the sandwich legendary back to its full powers.
All in all, this particular story arc is very good, despite the bland boss battles. It provides fantastic character development for both Arven and the Professor, and it is the direct link to The Way Home as the fourth arc of the main story. I just wish that the Titan Pokémon themselves were a bit more impressive.