It's still going to artificially inflate Edge's numbers from tech illiterate users that don't know how to change it. There's a significant number of users out there that will put up with Microsoft shitting down their throat before bothering to expend the few minutes it would take to learn how to change the settings themselves. The few that do try to figure it out will find Edge directing them to Bing which will make every effort to convince them not to do it. Meanwhile, Edge will steal all their bookmarks and tabs from Chrome, in order to further encourage users to just give up and use Edge.
It's all calculated "dark patterns" shit, and it works. Microsoft counts on these people being so easy to corral.
And you can bet your ass after they implement this, they will push an update that "accidentally" resets the default back to Edge for everyone. Just to "clear the board".
it stops malware from doing it
There are many different ways to prevent that apart from straight up removing the functionality. Another tactic Microsoft uses is trying to convince you there is only ever one way to secure the system and they "have no choice" if they want to keep their users safe.
It's like saying the only way to keep a plane from being hi-jacked is to handcuff every passenger to their chair. It's bullshit.