Ash getting stomped by Tobias didn’t have to happen though. He could’ve fought weaker legendaries instead of losing to just two of them.
As I said, that battle HAD to be a full battle, or do you all not realize that the previous battle against Paul was also a full battle.
Secondly the reason why Ash lost so badly although he fared better than anyone else in the league was because Tobias was that strong with that strong of Pokemon.
Now onto the battle with Kukui and Ash. Was it necessary for it Naganadel to come back? No. Was it necessary for it to be a full battle? No it could've easily been a 4 on 4, a slight step about the 3 vs 3 that was Ash vs Gladion.
There is absolutely NO reason for Kukui and Ash to have a full battle if Kukui and Ash's battle doesn't go down to the wire with their remaining Pokemon. Incineroar is strong, and likely Kukui's strongest Pokemon, there's nothing saying the rest of his Pokemon is as strong, so maybe Lycanroc loses, but Torracat wins, maybe even evolves to get that extra push out. Then it'll likely be another match coming down to the wire with one Pokemon on each side.
If Kukui were to sweep Ash's team, it would've been needless and pointless for the battle to be a full battle. And I also fail to see why Ash needs to lose so badly when he just became the Alola champion.