> Is "Debian desktop environment" identical to "GNOME" upon installation?
Assuming you install with one of the REGULAR installers (not one that contains the word "Live" anywhere in its name): yes. Selecting "Debian desktop environment" in the installer simply acts as an alias for whichever desktop environment task happens to be the default for that installer. Right now, for the regular official installers (and also for the unofficial installer with non-free firmware), that default task happens to be GNOME. With the "Live" installers, the default is different.