They are mostly used to shoot down cruise missiles deep within Ukrainian territory, not planes (Russian planes don't fly over Ukraine controlled territory anyway, that would be suicide, and over frontline they have decent AAA). There's nothing new in defence pods like Vitebsk-25 for aircraft, they existed for decades and even many civilian aircraft have them (like many Israeli passenger planes, knowing they can be subject to terrorist shootdowns).

The difference is training. Scores of operators on the ground are already trained and experienced on the Stinger platform and the development of complete already.

Backfilling a proven stock item is faster than infilling a new platform. Refer to the training cycles required for tanks provided by the UK. Those tanks have qualified operators ( with matching tactical-operational skills, but there are few personnel to back up their abilities. The Stinger is valuable because of the established user base compared to that.

Per the article, this production run is a stop gap. The next gen system they (US Army) want is not yet available. They're restocking to cover the interim.

The stinger works great against drones and cruise missiles. Whilst Vitebsk-25 may be on choppers and fixed wing aircraft, It won't be on Iranian drones. And having stringers take down the small stuff makes using the Patriot System most cost effective against bigger targets.