I did a quick search and could not find any information about the system... I mean they could have used standard 80mm rockets in tandem because of the length of the ground launchers tubes... that might have extended the effective range but I suspect they would struggle to match the range of the original Grad let alone the upgraded models.
The range given in the article suggest they are just standard 80mm rockets.
Double stage rockets would certainly have increased range and its narrow calibre would mean lower drag in flight, but a two stage weapon would be less accurate than a single stage weapon because of variations in separation and igniting the next stage would lead to a spread of rockets... so the extension of range would have been at the cost of accuracy and increase in price.
Having a two stage rocket would greatly increase range but also increase cost per rocket, but the critical thing is that even if you go for a two stage 80mm rocket and even if that did give you comparable range with 122mm Grads... the 4-5kg payload of the 80mm rocket means even with 80 rockets the effect on target wont be as good as say with a standard Grad rocket using the 9M218 rocket with a 30km range with 45 HEAT submunitions in each rocket.
The simple fact is that while 80 x 80mm rockets could put 400kgs of HE and fragments in 80 locations around the point of aim, a Grad vehicle could put 1,800 HEAT munitions around the point of aim with 40 x 122mm rockets. More importantly the max range for the 80mm weapons is not going to be more than 20km, while this 122mm rocket can reach 30kms.
I suspect their key selling features is light weight and low cost per rocket, but that really means they don't want the Grad they want something much lighter.
I have seen aircraft rocket pods lashed to the back of light trucks in other conflict zones including a 32 shot 57mm rocket pod on the back of a truck in Afghanistan in the 1980s. Not the most efficient weapon except at very short ranges in direct fire mode... and that is what I suspect we are talking about...
A weapon you can carry on the lightest vehicle... it can be hand loaded by anyone... and accuracy is not a huge issue when you basically aim the truck at the target... make slight adjustments to the elevation based on range and then just launch a volley of all the rockets at the target and then drive away.
The new box shaped aircraft pods the Russians are developing would be ideally suited to this situation, though that photo showed a reasonable sized vehicle with a Grad like array of rocket tubes on the back.
Would be all smoke and noise I suspect, but I would not want to have one pointed at me....