@Paul ******
not necessarily. Some embassies have it clearly stated on their website that you must remain in country until your visa is received. Embassies are starting to ask people to come in for interviews, want copies of all passport pages again and other weird little requirements that are changing daily. The only thing using e-visa system does is change the way you submit info and you don't have to hand in your passport. It doesn't change the fact that people are "expected" to remain in the country they applied to for the duration of the process.
Have people left countries before getting receiving the approval? Yes, some have been successful doing this but more importantly others have been denied and lost the visa fee. It's not as cut and dried as you suggest. The OP should know there are risks associated with leaving.