Well this is not true. The real reason behind the problems is your Operating System (or parts of it). If you would google Fmod issues for development you would quickly realize that microsoft messed it up. In every developer space there is problems with it. Soundengineering, gamedevelopment etc.
First problems with diablo3 however showed up when microsoft introduced windows 1809 with an updated sound system. (oct 2018)
Back then setting the soundchannels to “lowest” ingame fixed the majority of issues.
Diablo3 is using fmod as Sound engine, which relies on c++ libraries currently using the 2015 distributable. Since win10 2004 released 6/2020 microsoft decided to change how distributables work, they merged the 2015/2017/2019 C++ Redistributables together so that you would only ever need one of them and not on a specific location. At this point everything started to escalate pretty hard.
The lag/freeze that occurs is just the delay/inability of the Fmod.dll finding its library counterpart on your disk.
All games using Fmod as sound engine are more or less affected, a list of games that are using fmod can be found on the fmod wikipedia entry (its alot cant post links)
League of Legends for example switched its sound engine because of this.
Using a windows 10 version prior to 1809 fixes close to every major problem with the game. Such as Fmod delay and not properly working ingame FPS cap.
There is nothing Blizzard can do, but maybe switch to a different sound engine. Its not the games fault, its microsofts.
But you yourself can do alot of things. Running win10 1709 or find a c++ package that places the files at a place easy to find for your fmod.dll. I got one, but since its based on an executable that also does a little more i really shouldnt share it on official d3 forums. But i give a hint its available at majorgeeks