ENodeB does not modify QoS parameters for a bearer whether it is default or dedicated bearer.
Based on application, UE triggers "Bearer Resource Allocation Request" NAS message to request network to create a dedicated bearer. Now network based on subscription details present in SPR (Subscriber Profile Repository), it decides whether it should initiate "Dedicated bearer creation or not".
Dedicated bearer creation can be initiated from network side also such as VoLTE call. In VoLTE call SIP messages gets exchanged between UE and SIP nodes and after that application function node (AF) initiates dedicated bearer creation by initiating AAR message to PCRF.
In short, eNodeB does not know which application is running between UE and network. For eNodeB, it is just a radio bearer.