The note describes, only Z: drive is available to upload/download files, when on ITS (HTML WebGUI).
Example of a Z: drive download:
Yet, with APC, SAP has implemented a seamless method to generate a printout and download that print file, without using Z: drive (Ref: 2159422 – Front-end printing for SAP GUI for HTML with ABAP Push Channel). So, I believe, the restriction that is mentioned in 2547717, can easily be circumvented, especially for downloading files.
Below is how I downloaded files, without Z: drive. This may be just considered as an example to motivate SAP to standardize a better approach, than using Z: drive. Because of the variables available to me from an ABAP standpoint, I couldn’t find a way to make the download behavior same in IE (Version 11.2791.14393.0) and Chrome (Version 72.0.3626.109), using the same code. This is where I feel, SAP can do better, without depending on Z: drive.
Note the following changes required in IE vs Chrome, to make the download behave the same way. For now, since there is no SAP support to handle this automatically, you may configure a parameter ID, that the user can set, for his preference on the browser and change the values accordingly.
Chrome code: (note the marked lines)
IE code: (note the changes to url & window name)