The "spanish air traffic controller" he is referring to is known as "Carlos," and, according to the Spanish, does not actually exist. The Russians made him up out of thin air.
The Russian "radar reports" claim that the SU-25 was flying "on the same level" as the airliner, which is physically impossible, since the SU-35 cannot climb up to that height. The closest an SU-35 could get to the airliner is 3KM, and that would be directly below the airliner.
Next, the cockpick they are referring to was sawn in half and most of it pilfered by the Russkies themselves. What evidence is this guy referring to? Most of it is already gone.
Lastly, the "expert" appears to not be anyone actually there, but someone looking at a random photo, and this, while vomiting up Russian propaganda that was old several days ago. The British have already stated that the evidence from the blackbox suggests it was hit by a SAM due to explosive decompression. Bullets would not destroy an airliner like this and spread its parts for miles. Only a missile would.
It's probably best not to fall for any random BS put out by blogs.
I also do not think a pilot would attack a jet from the side, as your window of attack is greatly diminished. You would be on the jet’s 6 and fire a burst at the engines.
I think you made a typo in your post, and meant to refer exclusively to the SU-25 Frogfoot, which is unpressurized and has a service ceiling of only about 23,000 feet, and believe it or not, the SU-25 cannot equal the top speed of a Boeing 777.
It’s my understanding that the service ceiling of the SU-35 is +/- 18,000 meters (about 59,100 feet). The rate of climb is greater than 280 meters/second (51,000 ft/minute).
The SU-35 or the SU-27 could have conceivably done the deed, but as you point out, not an SU-25.