Wait, the old one wasn’t wonky? First, to be clear: you’re using the -ViewCaptureToFile. That first dialog box needs a full path to where you want to save it (e.g.: /Users/rhinorudi/Desktop/foo.png) in order to work. Second, the non-dashed command actually asks you where you want to save the file before showing the command options - leading many to believe (understandably) that you can’t specify resolution, etc. Third, we’re inheriting this wonky behavior from Rhino for Windows, fwiw. Other than that, the command works fine 
See: RH-28772
No, wait, TL;DR: This is how it’s supposed to work. Changing it would break scripts.
Sorry, just airing my frustrations with how this command “works” …can you see a way out of this bind?