When I first found out the plot of this episode when it was released in Japanese I was apprehensive about it, mainly because it confirmed the writers were taking a path I thought they wouldn't. They've put Sawyer on an equal paring to Ash, which not only makes the narrative inconsistent, and making Ash appear weaker than he actually is. This was my problem by some parts of the BW series, namely the first tournament so it's unfortunate it's been repeated here. I have four criticisms of the episode.
Firstly, Sawyer is unrealistically overpowered. This kid started out as a novice, now he's spamming Clawitzer and Sceptile and has managed to beat Ash. Not only was this a reasonably comfortable win, it was actually party due to decent strategy. In the second battle managed to work out what Hawlutcha was going to do and had a plan to defeat it - this is the same kid who didn't know dragon moves are ineffective on fairy Pokémon.
He's also one gym badge ahead, despite starting three behind. Even considering Ash has Clemont, Bonnie and Serena slowing him down and had to spend time at Serena Masterclass (I knew going to that was a mistake) his turnaround in strenght. His progress seems like going from loosing a school swimming carnival to competing and winning against members of the Australian Olympic swimming Team (which considering London might not actually be that much of a stretch). Ash is a competent trainer - the series should reflect that more often.
Secondly, Noivern. This is the third time it's battled since it evolved, and despite it's initial win against doublade, it went down fairly quickly to Sawywer's second Pokémon. So far this series I think it's had four battles including both of Sawyer's and three have a been losses. Ash remarked that it had gotten stronger since evolving - That is unfortunately not supported by it's record.
Thirdly, Greninja spamming. Greninja may have lost to Scepitle but it still held up the battle for Ash, by defeating Clawitzer. And as with the previous Diantha and Alain espidoes it's undeniably the focus. It spent longer on screen than the other Pokémon, won a battle against an unnamed trainer just to remind us of it's strength and worst of all, Hawlutcha is sacrificed simply so Greninja can have a small extra moment of glory. Slightly unfair this is the first time Hawltucha has had a serious battle since prior to the masterclass.
Fourth, Bonnie's singing. Either the voice actor can't sing or is trying to sound too much like a child, but the singing is irritating. It's trying to be cute, but fails dramatically for four reasons. 1) Bonnie's singing voice is, well just like a child, high pitched and off key, with pointless silly lyrics. 2) There's something off about singing to a Zygarde core. Singing to a Pokémon that is cute of is portrayed using a woobie trope such as Oshawott or Pikachu, would be cute. The Zygarde core is a legendary of unimaginable power. It would be like singing to Rayquaza or Aceus. 3) To make the singing work as a scene, the trainer and Pokémon need to have an indentifable bond. Ash singing to Pikachu would be adorable, because they're clearly close to one another and Ash's affection for Pikachu is established. The way Bonnie and Zygarde have been written come across a little girl picked up a legendary Pokémon off the ground and started playing with it like a doll. The notion of friendship is false because it's one sided, Zygarde doesn't openly show affection to Bonnie. 4) Bonnie, saying it has you isn't going to make Zygarde feel better about the other core being locked in a cage by a group of terrorists.
That aside, the battles are good and Sawyer's still a cute character. He has a certain innocence, good nature and determination that even though he is not the protagonist endears him to the audience - which I suppose is why people were rooting for him to get mega Sceptile and why ultimately this episode will probably be viewed favorably. In particular the part where he thinks to himself 'I know I have eight gym badges but beating him will prove I've become a fully fledged trainer' gives Sawyer a strong combination of self-doubt but also of determination that allows the audience to feel happiness at his success.
8/10