There are two things going on here. One is that any command consisting of a direction (with no verb) is interpreted by the parser as “go”. There’s not much you can do about that, as it’s hard-coded in the parser.
The other thing is that the standard directions have their usual abbreviations, “e” for east and so on. This is fairly easy to override — you can just replace the section of the Standard Rules in which those abbreviations are defined.
Create a section in your code called something like
Section - Directions (in place of Section SR1/4 - Directions in Standard Rules by Graham Nelson)Then go into the Standard Rules, and copy and paste Section SR1/4 (without its section heading) as your new section. Now you can edit it to get rid of the abbreviations.
Of course, this will have the effect that the player can never use “e” to refer to east. But if you’re 100% choice-based that won’t matter. If you were planning a mixed-mode choice/parser interface, you might be able to use conditional understand statements to allow direction abbreviations just when you wanted them.