Changing the game rules (aka the sv_x variables) by executing a config file in game via the console doesn't work.
Example:
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I've got a config file named dmpure.cfg in my ZDoom dir. It includes the following settings:
- sv_nofov 1
sv_nofreelook 1
sv_nojump 1
alwaysapplydmflags 1
Then, I launch ZDoom & type "exec dmpure.cfg" in the console. The config is read, but the only setting that's applied is alwaysapplydmflags.