While I agree with your general sentiment, note that at least in ML-class, you can resubmit quizzes as many times as you want for full credit. Thus over the course of an hour you can retake the quiz enough times to brute force a perfect score without breaking the letter (and arguably the spirit) of the honor code.
The Programming Projects that ML class had were slightly better metric of performance as there's more work that would have to be plagiarized, and if you're just going to go through life outsourcing all of your work then I guess that's your prerogative. However, I think that if you wanted to be very serious about actually testing for knowledge of material then the addition of some sort of interview component (phone/skype session), while time-consuming, could help.
In a way, yes, the programming projects in ML seemed like a better measure of performance in that you have to actually figure something out. However, they have two (sort of) disadvantages vs normal homework:
1) you immediately know if you got it right or wrong when you submit, so you can to a lesser extent brute force the correct answer
2) with the exception of maybe the first assignment, they are all "fill in the blank" sort of programming assignments. You basically just have to find the equations they give you in the PDF, translate them directly to Octave, and bam you're done.