The chemistry of mixing sealants
If your tire has begun to lose air slowly (loses 10 PSI over 2 days), it has lost the liquid carrier in your sealant. The remainder of the sealant is dry or lumpy and can't travel to the new thorn. It was ammonia or environmentally friendly antifreeze (not ethelene glycol) that evaporated. Like the original liquid is pretty much gone.

Our riding club carries Orange seal and Stan's in portable 3 ounce bottles. We use it interchangeably any time a member gets a low tire on the trail. Never had an issue.