That's not good news. Not having to waste previous dev time dealing with lags is exactly the reasons to opt for such a 3rd party platform in the first place.
I'm not saying that Spatial OS is causing this lag. Before today I had never heard of that game. It's the only game I found when I googled for "Spatial OS MMO". I haven't played that game. I don't know how big the performance issue is or how long they have been having it. Maybe it's just one of those - oh so common these days - we're out of money, we'll release the game.
Years ago, I backed a kickstarter campaign for a MMORPG that used Hero Engine. A few years ago the devs of that game switched to Unreal Engine, because of issues with Hero Engine. Those devs didn't have enough money, so they used all the assets they had created to make a survival game and put the MMORPG on hiatus. Recently they sold the MMORPG to the owners of Hero Engine. That MMORPG will probably be finished at some point in the future, but it won't be the game the original devs promised. Of course Hero Engine and Spatial OS are two completely different beasts.
I've had some disappointing experiences with all kinds of games I backed on kickstarter or purchased in early access. These days I back merely because I want the devs of a game to have a chance at trying to make the game they want to make. If we don't do that, then all we'll ever get to play in the future will be cheaply made one man indie games and big budged games made by economists/psychologists.