Mallow is Hurley from Lost in terms of how long we had to wait to get a focus episode that shows her character's background. In Season 1 of Lost, in episode 1 the main characters' plane crashes on an island, with no backstory of who any of them were before the plane crash. As a result, each subsequent episode focused on one character and told his or her backstory. The character of Hurley was left until last, not having his backstory revealed until episode 18, which in an American serialized drama is super-late, almost near the end of the season.
In this rather unique season of Pokémon with Ash being thrust into a group of people who are already companions with each other, rather than meeting them one by one and their giving reasons for wanting to travel with him, backstory episodes are required, and we got them for the others in episodes 5, 6, 8, and 11, (although Sophocles's episode told no backstory and was trash), and now Mallow's first focus episode was left for last, coincidentally episode 18 like Hurley from Lost.
EDIT now that I've finished watching the episode: I'm surprised they didn't just think to ask Lillie's butler to allow them to use his Oricorio to help out. Mallow's clearly mad tight with Lillie and visits there all the time.
More importantly, Bounsweet's evolution is massive. It proves that they're willing to evolve a cute out-of-ball Pokémon, so I'm really hoping it means Rowlet can evolve despite spending most of its time out of ball
A further EDIT now that I've read the whole thread and have things to respond to:
I will be disappointed if they kept this evolution sequence a one-time only thing, especially since they have NEVER done that before.
Even though it was not the same because it still had the blue glow, Eevee into Sylveon had Sylveon's ribbon coming out of Eevee's neck before the rest of Eevee's body started evolving.
I really don't understand the people saying it is no big deal.
If any other series did it, people would be praising it as the best series, but since SM is doing it, people are acting like 'meh, it's nothing special, it's obvious'.
It was a big deal of internal continuity when DP had a massive recurring cast who kept reappearing. Just think back to AG and how May had COTD rivals at almost every contest, for an example of how Gens I-III didn't have much internal continuity.
It's not a big deal anymore to have internal continuity since DP, BW, XY all did that for three straight generations now of having massive recurring casts (BW until episode 108, and the whole saga for both DP and XY)