To have increased capacity for tomorrow, they'd need to bring back and re-train/refresh a whole batch of servers, re-configure restaurants, and make adjustments in the kitchen (where they are also practicing social distancing). When Disney does eventually move to increase restaurant capacity, expect it to be slow and steady. They're not going to go from 50% capacity (where they're at now) to 100% overnight. That would be a logistical nightmare.
The availability this morning was an error -- a really big error caused by some routine maintenance they were doing overnight. Now that they've corrected the availability in the system, they're trying to figure out what to do with the reservations from this morning. Am I saying all reservations made today are going to be cancelled? Not necessarily but I wouldn't take a chat CM's response as assurance they won't cancel or adjust any reservations from this morning.