And that training claim is complete hogwash. You target-lock enemy planes from miles away. There is no way you would see the plane you're targeting.
Ok so, there's a few things to take into account here. Part of my job as a US Marine (many years ago) was sortie communications. Part of THAT includes understanding how and when fixed and rotary wing aircraft "talk" to one another.
The type of targeting you're referring to, is generally used by ground and sea based platforms. Before those systems are engaged there are several several several attempts to contact unknown aircraft which we'll get to ina second. Aircraft rely on short to mid rage radar and radio. (See FSX image below)
There is a difference between being able to SEE a target at mid to short range and being able to engage that target and mid to short range. The targeting actually takes place inside the ordinance and is relayed to the aircraft and the pilot via the computers and HUD inside the cockpit and helmet. The distance a target can be engaged by AA Missiles (air to air) is limited by the ordinance.. mostly by the fuel it can carry. Im not an ordinance guy but I think the furthest Id heard of an AA missile being fired and hitting a target was like a mile or two, but again we'll get to that in a sec.
There are several different types of radios on the aircraft but the three most common are IFF, SQUAWK, and Voice (Pilots, feel free to correct me here). For our purposes here, we're going to be focusing on IFF or Identification Friend or Foe. MOST countries (and this includes the Russia and its Federated States) will attempt to contact any unknown aircraft BEFORE they blow it out of the sky. An aircraft is unknown if its SQUAWK and IFF dont match any listed flight plans. BELIEVE me.. this doesnt work like you see in the movies, the military KNOWS what sorties it has up and running, who they are, what their SQUAWK and IFF should be.. and they're both very VERY hard to fake.
So lets now imagine that the US does somehow fake Russian IFFs or SQUAWKS. The Syrians are not stone age barbarians, THEIR pilots know the difference between an F-18 and a Russian SU.. the profile (the sides, front and rear) of the two aircraft are completely different. Things like the tail fins, the air scoops, the armament configurations are known.. its how you visually ID an aircraft and not shoot down a friend.
Now lets go back to your idea about shooting from miles away. Fighter pilots are trained to visually identify and aircraft BEFORE they blow it out of the sky just on the off chance that its NOT a threat. Yes, there have been mistakes in the past but those usually civilian airliners being shot down by military aircraft because they failed to respond to repeated calls for contact by the fighter aircraft, or ground/sea based radio calls.
This brings me to Rules of Engagement. Military Aircraft and pilots have ROE just like ground troops. They will engage and fire ONLY when certain criteria are met. PART of that criteria, because of the tragedies with civilian aircraft, is to visually identify your target before you pull the trigger. At that point, the jig is up, the US Aircraft have been IDd by the Syrian Airforce and the "false flag" no longer exists.. period. Syria would be all over every news outlet they could get their hands on saying that the US had invaded and were trying to pass off as Russian Aircraft. The US isnt that stupid. It would literally make MORE sense to buy or steal Russian equipment and fly it to blame the Russians than dress up US fighter aircraft to try to pull that kind of stunt off.
So no, the training scenario is completely and totally legitimate. During dog fight training, the US very regularly uses US Equipment to SIMULATE another country's equipment. They take an aircraft with a similar flight and maneuverability profile and train US pilots with them so that they're used to dealing with a fighter that moves like those targets. Train like you fight, fight like you train.