Every opinion can be respectable, but not the opinion that the advantage could be of more than 3 minutes. You start with the idea that Boston can penalize top runners of about 2:00. But we have many examples this is not true.
Where did Joan Benoit run 2:22, in a not windy day ?
Where did Gelindo Bordin beated the Italian Record after winning Olympic, running in 2:08:19 without wind ?
Where athletes as Benjamin Maiyo had their PB, in not very good conditions ?
I had athletes winning Boston 3 times (Elijah Lagat in 2000, Rita Jeptoo in 2006 and Selina Kosgei in 2009), and always their results was influenced by the tactic of the race, not from the course. In 2006 Rita ran the last 7,195m faster than all the first top men, because the race before was not very fast, and in any case she improved her PB.
What I want to say is that an hilly course can have different impact for different athletes, but in some case doesn't penalize the final time. Athletes as Geoffrey (very high agility) or Moses (very high eccentric strength) don't suffer this kind of courses.
Leonard Komon, for example, improved last year the WR of 15 km in a race called "Seven Hills", that of course is very hilly. If there are not long hills to climb, but short and hard, athletes with good strength can attack at high speed, and the next downhill can be run at high speed with good relaxation.
Women suffer more the conditions of Boston, because have less strength. So, personally I'm not sure that Boston can penalize of 2' the athletes.
Second point : Geoffrey ran last year two marathons in 2:04:55 and 2:05:10, and currently is very much stronger, expecially under the mental point of view. So, there is no reason he could not run, at the moment, in 2:04 in the same races of last year. Why somebody continues to think at his time like a 2:06 in any other race ?
I explain Moses was in a shape for 2:04. The only doubt was his reaction in the first marathon. Since he was amazing under this point of view, his result is totally normal, looking the resultances of his training.
I'm sure that the same athletes in a fast marathon with the same weather conditions (but without wind) could run under the WR of Gebre in Berlin. So, my personal evaluation of the advantage is no more than 40 seconds, because we know the real technical value of the athletes, and cant be surprised from their results. If we had athletes as Duncan Kibet able running 2:04:27, there is no reason because somebody can have doubts about the possibility for Geoffrey Mutai to run one minute faster. About Moses, I advice anybody to wait and to see the future. But never happened in my life rhat a my athlete could end his career with a PB in his first marathon (I think the best must come after 7-8 marathons, if the training is correct), so I think he can have good room of improvement, because I know what he did, but I know what he still didn't do, that in my training phylosophy is important for reaching the personal best.