This is not a bug but rather a natural consequence of how a Visual Overview is initialized. InitVar shape data is processed synchronously with the creation of your Visual Overview.
Meanwhile placeholders such as the property placeholder require us to do a request to the server. Because we don't want to be blocked until the server responds, we do this asynchronously.
The consequence is that InitVar can't use the property placeholder properly, as it doesn't have the value yet.
You can work around this by using the Execute shape data, along with the ExecuteSetsOnInit option (in the options shape data) and the ValueChanged trigger. More info can be found on our help pages