Dr. HHH quotes "4 weeks isn't quite conclusive (about 98-99% reliable". Considering there is nothing called 100% in medical science, this is certainly is good enough for most people here with no to low risk. In fact, no expert online or I personally know quotes Duo to be 100% at 28 days, it is always between 94%-99%. Therefore, I don't see any change in the original information, I would still accept a duo conclusive at 4 weeks.
Now, if you want to achieve that final 2%, waiting for 2 weeks wouldn't be a bad idea. That's worth the buffer. However, its very unlikely that 4 weeks negative with a duo would change ahead.
I also see that different sites would want different approach from the doctor, I have been on this site for more than a decade and the reason I've been here is because of the practical approach this site has always had, it has helped thousands of worried well. Maybe this other site has a little conservative approach that needs Dr. to comply with. Hence, he is recommending 6 weeks for 100%. I have always seen him to quote duo to be between 94%-99% here on medhelp, there is no surprising information.
Nothing changes, it's just two different routes to arrive at the same thing. I don't see a point to unnecessary discuss this any further.