You need to try a really good set of classic earbuds to see what you are missing between the type of buds you are talking about. While the fruit devices are indeed open sounding, they are still limited on the soundstage and separation compared to true earbuds (which is what the Linkbuds are) because they are still directed by a narrow opening into the ear (they are more like an open IEM than a true earbud), whereas an earbud is round, sits outside your ear, and you hear it much like you would a set of speakers. Basically Sony created a set of classic earbuds that are TWS. I honestly don't think they overengineered these at all if you understand what they were trying to achieve with these. I don't think they were trying to copy the Airpods (but just more complicated) at all, but were trying to make true classic earbuds while having TWS.
While classic earbuds are a niche thing nowadays, they are still VERY popular (and for good reason). Take some of the best open back circumaural (over-ear) headphones, and shrink them into IEM size. IEMs and even semi-in-ears cannot match that staging; though semi-in-ear buds can come much closer than IEMs can.
Also, I wouldn't trust those graphs for any open or even semi-in-ear earbuds. Those measurement rigs were set up for IEMs and depend totally on a good seal to give accurate readings. And make no mistake, most TWS that have tips on them DO indeed rely on a seal to get their full sound whether shallow insertion or deep insertion is the intent.
There is no really good solution for measuring open earbuds yet. You can do a search on
this thread where there is a conversation about this very thing. The actual bass on the Linkbuds is nothing like it is shown on the graph. Granted, they will never reach Harmon levels of bass (read bass boosted), but this is the nature of open earbuds (though there are a few pairs that do VERY well, and can almost rival IEMs for quantity of bass), and until recently has also been the nature of open back headphones.
The Linkbuds actually sound a lot like the graph for the Airpods shows. Very full mid-bass and up, with sub-bass roll-off, though it isn't void and IS there.