How to send two *.glyphs paths to from open -a command?

When comparing 2 *.glyphs files using, you usually open them from GUI.

With other application like, I sometimes open the file(s) using following command from
open -a <Application> <file(s)>

I did it with the with 2 glyphs files, but opens the 2 .glyphs file to 2 separate compare window and each window loaded only 1 glyphs file (i.e. no comparing counterpart loaded) like:
open -a Font-01.glyphs Font-02.glyphs

Is there any solution or workaround of this kind of operation?

I tried several times and found sometimes could open 2 files in 1 compare window, but sometimes separate 2 windows…

When is not launched, open -a command lunches app and load 2 files in 1 compare window.

When is already launched with or without compare window, open -a command load 2 files in 2 separate compare windows.

You want to open MergeGlyphs with two .glyphs files in the same window? This works for me all the time:

/Applications/ --args ~/Desktop/file1.glyphs ~/Desktop/file2.glyphs 

open -a Font-01.glyphs Font-02.glyphs works fine for me if it is open or not.