BINDABLE properties still need NOTIFY as a fallback (afaik, the qt documentation doesn't mention it either way so I keep NOTIFY)
Also this is going to have issues due to qobject threading, as it will create a direct connection. Take a look at how FileViewOperation::finished works and is called.
Should trigger quantizeAsync(). You can use QQmlParserStatus::componentCompleted to delay the initial run until all properties are set as well.
This is a race condition, if another quantization task is started before this one finishes the new one won't run. Instead of canceling with isProcessing, keep a pointer to the old task to disconnect from before starting a new one.
In general also use auto x = y syntax over T x = y, and avoid T x(y).