MSIX App Attach is a new process for AVD/WVD to layer applications on top of your image that occurs on user logon. Microsoft guidance is this process should be fast, but MSIX apps are sitting on remote file shares -- these shares can be overloaded (say, AV running on them consuming all the CPU) or have high latency (misconfiguration -- eg, pointing to the wrong share?). With that we don't know if the AppAttach 'layering' will be a logon blocking process (like AppX packages), or a async process (consuming CPU/network/disk resources during logons).
MSIX App Attach is a new process for AVD/WVD to layer applications on top of your image that occurs on user logon. Microsoft guidance is this process should be fast, but MSIX apps are sitting on remote file shares -- these shares can be overloaded (say, AV running on them consuming all the CPU) or have high latency (misconfiguration -- eg, pointing to the wrong share?). With that we don't know if the AppAttach 'layering' will be a logon blocking process (like AppX packages), or a async process (consuming CPU/network/disk resources during logons).