xdg-scheme-handler doesn't open script with same terminal that launching it from a desktop menu does

I'm trying to set a x-scheme-handler URI for my python application. This application is launched via a shell script in /usr/bin. I've had a desktop file for a while, and it's worked fine, opening the program in the KDE terminal, Konsole. I just added the MimeType=x-scheme-handler/iicalc; to the desktop entry, and did xdg-mime default iicalc.desktop x-scheme-handler/iicalc, and the custom URI works, it runs the correct script. The problem is the it doesn't open in Konsole, like launching it from the application menu would. Instead, it opens in xterm, which also happens to be what my $TERM variable is set to. How can I make this behave in the same way launching it from the application menu would, while also working cross-platform? Here's my current desktop file:

[Desktop Entry]
Version=2.3
Type=Application
Name=ImaginaryInfinity Calculator
Comment=Expandable calculator
Exec=iicalc %u
Terminal=true
Icon=/usr/share/icons/iicalc.tiff
Categories=Education;Office;Utilities;Math;
Keywords=calculator;math;
MimeType=x-scheme-handler/iicalc;