Not necessarily. They get more of the profits, but there's less profits because Divinity is not as big of a name as DnD. But I could totally understand not wanting to be beholden to WotC.
Solasta is DnD5, but it cannot really market itself as such, so... if you're at that point, why do an off-brand DnD side-story instead of making it a Divinity side-story.
They could use their Divinity IP but the system & engine they developed to support 5E. Basically a 5E game set in Divinity. Would make a lot of their existing followers happy & would retain a lot of the new fans they brough in with BG3. Plus they wouldn't have to either pay or share revenue with WotC (we don't know exactly what the current deal is, or when it expires).
BG3 was in development 6 years. I can't imagine their existing license with WotC will include much if anything beyond BG3.