A big problem with balloons is the much lower altitude, requiring many more to cover an equivalent area (horizon is much closer).

Also, currently balloon relay technology has thus far proved impractical for long term, high reliability coverage, with longevity and long term station keeping being thorny problems.

Meanwhile, Russia understands well Molniya orbits, having used them for decades. So it wouldn't surprise me if indeed these new satellites are destined for such.