I'll take devil's advocate point on this.
Is there an source for this? I really doubt this, as 1991 showed how vulnerable A-10 was against any competent air defense system. Even Iraqis could prevent A-10's from working when they had their TO&E strength air defense, in a terrain resembling a bowling alley, in almost perfect weather, so I doubt very much there was any fear from A-10's in any level of Soviet professional military staff. See Gulf War Air Power Survey available via USAF for references.
As for original WI, if no dedicated ground support aircraft, like Il-2 Sturmovik etc. were developed, I think wars would have been faster for the opponent which had air superiority. Instead of wasting valuable flight hours for very limited gains, the flight hours and bomb load could have been used far mor efficiently. CAS has always been very dumb use of flight hours. Thus only a very few dedicated CAS airframes have ever been built. They have been mostly failures, like Su-25 and A-10. In 21st Century any airframe is CAS airframe via use of GPS guided munitions, so CAS airframes are now a waste of money and effort as they were before.
I'll take a case example of CAS fallacy. In Karelian Isthmus in 1944 when Soviet Union attacked against Finnish positions the initial defense position and the planned main defense position were crushed in succession with succesful artillery-tank co-operation. However, instead of acting like during the Winter War, the Soviet Air force dedicated themselves to close air support. As a result, enough Finnish reserve formations and artillery could be brought from between Lake Ladoga and Lake Ladoga to form an yet another front, which held. An another effect of concentrating on CAS was that Soviet Air Force could not prevent Finnish Air Force and Luftwaffe interdiction sorties, which had a deadly effect.
Of course we have not even touched the attack helicopters yet, which were quite efficient in Algeria or early Afghanistan but not anywhere else.