I'm not. I was in Argentina when River was relegated though (or rather, at the border right after it happened)
Well in total attendance you can't say River is breaking records due to the nature of Primera B teams, but they are selling out, which can't be said about Boca this year. Part of it is the novelty factor, but also River fans travelling because of the stadium ban and fans throughout the country supporting the team through this. It's hardly just Patagonia (there's only one Patagonian side in the B anyway) - in Mendoza, when River played Independiente Rivadavia, they held it in Godoy Cruz's stadium so they could sell more tickets.
I have to credit Boca unfortunately, they did dominate this apertura - it was a very workmanlike team, but it constantly got results. River could have used a team like that last year. But the Primera has definitely seen better days. Right now 7 of the top 20 clubs on the all time table are in the Primera B, not just River but also Rosario Central, Huracan, Gimnasia La Plata...and in the Primera, San Lorenzo is in the middle of a massive crisis and is risking relegation too, and other clubs like Banfield and Velez were plundered to become shells of themselves. But still, Boca only allowed 4 goals - that's ridiculous.