% agree with what you said. Plus imo the transition of the earings to a necklace has such a huge significance to their relationship!!!
Like it feels like a promise ring with the intent of marriage between the two one day, especially if we parallel it to the matching necklace to engagement/wedding ring of Kabakura and Hanako.
The fact he couldn't wear them at first because the holes closed up, kindda alludes to the fact that their relationship is still very new and tentative. But now that they're both so sure and solid about their relationship, she still wears her earings and he can wear it as a necklace. They're similar to their besties, but they're also quite different and have their own pace. I also find it kinddda healing on Hirotaka's part because he got the piercings in the first place because he was jealous and wanted to be Narumi's ideal bf. He doesn't have to change who he is to be with her.
I've seen people keep complaining about the ending between Narumi and Hirotaka but the manga has always been paced like that. Koyanagi and Kabakura have been dating for YEARS and the manga ends with them being able to start a family. Narumi and Hirotaka only got together at the beginning of the manga and the manga shows them adjusting into a relationship after being childhood friends and slowly becoming more comfortable around each other in a new perspective. Which is why I feel like the story ended with them being able to share a first kiss since for them, they saw each other as friends for the longest time and struggled to realistically adjust to dating status throughout the duration of the story. Meanwhile with Kou and Nao, those two were primarily focused between their friendship and the story ends with them being able to become a couple. The story depicts each couple at different stages of their relationships especially with various unique personalities. More cute moments between the main couple would've been sweet however we've seen what happens when manga authors end up making too many volumes or work too long on a series.. let's remember the author has been working on the series for 6 years including during COVID. I think the story concluded quite beautifully and I enjoyed re-reading it.
Only thing I wished the story did was introduced the parents. Would've been an interesting plot point to see their reactions or views on otakus and their relationships. But I liked the ending and felt it was clever the author wrapped it up the way she did!!