The answer to this is actually the essence of how we do things differently from other platforms to the benefit of sound quality. Allow me to explain.
I don't know how large your QNAP library is, but let's assume it's a good few terrabytes in size and let's also assume the NAS has fast processing specs and the network is very fast and well-connected.
The easy way to make NAS rescanning faster is simple: add bigger processors and devote more system resources. The problem? This has many implications for a negative impact on sound quality. Also, real-time NAS refreshing/rescanning also requires the system to be constantly executing tasks and constantly polling the network, which also creates noise and will always be consuming system resources.
We are focussed on critical listening and want to make the sound as good as possible, so it is design choices such as avoiding these issues above that helps give us our sound quality edge, even if that comes at a trade-off of ultra-fast network scanning etc. Instead, we need to be more clever and efficient with optimised coding which we are improving all the time so that there is still a strong convenience factor.
As an aside, this is why systems with built-in storage are generally more optimal than using a NAS, as it bypasses a lot of the issues described above.
Do note that other software platforms may indeed be performing system tasks in the background, but are being more discreet in notifying you about that - we take an approach of making the user very aware when any significant task is taking place at all.
My suggestion in these scenarios would be perhaps to leave the rescan running overnight so that it does not interfere with critical listening sessions.
Hope that helps to explain!