Installed Engine build times, set:GameConfigurations="" question

I’ve been using “Installed Engine” method of building UE5 for a long time. Lately I decided to play with parameters to see if I can optimize the process. However there is a problem with build times, it is not working as expected. There might be a buggy situation.
Our interest is specifically GameConfigurations parameter.

The build command I use is below:

./Engine/Build/BatchFiles/RunUAT.bat BuildGraph -script="./Engine/Build/InstalledEngineBuild.xml" -target="Make Installed Build Win64" -set:HostPlatformOnly=true -set:GameConfigurations="" -set:WithFullDebugInfo=false -set:WithDDC=false -set:SignExecutables=false

Pay your attention to -set:GameConfigurations="" part. When I check InstalledEngineBuild.xml file, default value for GameConfigurations is Shipping;Development;DebugGame

I tried with several -set:GameConfigurations= arguments and here are the result:

Shipping: 20 minutes
Development: 20 minutes
Shipping; Development: 27 Minutes
Shipping;Development;DebugGame: 39 minutes << Should be default value
Shipping: 19 minutes
“” : 8 minutes <<<<< Which configuration is this?
nothing: 40 minutes <<<<< Default value*

I can reproduce the results.
So typing nothing and default value seems identical: (“Shipping;Development;DebugGame”)

Then what does set:GameConfigurations=“” mean in this case? What happens with this empty string argument? Is there a configuration like “no configuration”?