Well I am sure many concept has been tested with Iz 30 engine else they wouldnt be building it in first place , I think its part of risk mitigation to see if the Design Bureau can build an engine of the desired thrust based on existing technology and hence that can improve confidence that it is doable in the desired time.
Engine Development generally takes 15 years for new gen engine so it generally started before fighter development that takes around 10-12 years wrt to advanced countries like US , Europe Russia.
But the new engine or 2nd stage as they call it has many innovation including lesser stages , newer materials and the designer also mentioned Variable Cycle Engine as one of its targets with new design.
The 117 engine itself is a very modern engine with 70 % new components/parts compared to 117S engine used on Su-35S , The 117 can be compared to similar generation as EJ200 with slightly higher T/W ratio.