Unable to silently/unattended install with Windows installer.

[3hQyrpzdAWztAOoXJhsd]

1. Download the 2.19.3 installer from https://github.com/agraef/purr-data/releases/download/2.19.3/purr-data-2.19.3-mingw-x86_64.zip.
2. Extract the exe file from the zip.
3. Run the exe with the following switches:

Purr-Data-2.19.3-20230725-rev.e9fca4f8-x86_64.exe /VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP-

I'd expect the installer to run without an UI or prompt and install, but you get a popup saying Note: The installation will now start. with an option to click OK.

I've tried creating an answer file, but it didn't help. Going through the documentation at https://jrsoftware.org/ishelp/index.php?topic=setupcmdline I can't see any other useful option to suppress the prompt.

Is this intentional, a bug, or am I missing something to suppress it.