The way the schedule is made for whatever reason is they save most of the divisional games for later in the year. I've heard this myth in 4 or 5 threads also(1 in particular where it basically got repeated for 3 pages straight). At the end of the year sure maybe the top Atlantic teams may benefit but they haven't right now.
Not sure how much I'd say teams like Boston, Tampa and Montreal have benefitted either. Sure they have a lot of points against those teams, but the games aren't drastically higher than a Toronto and a lot of non Atlantic teams(2 or 3 more), they've just done a better job at taking advantage of them. I guess maybe benefit is the right word, but it just feels wrong, oppurtunity to benefit feels more like the thing we should be measuring. If 2 teams played 12 games against bad teams, 1 team went 12-0 and the other goes 6-6 it isn't really fair to say the first team is higher in the standings because they'd beaten up on bad teams more(which is true) when the lower team had the same opportunity to but failed to achieve the same success. I feel like pure games played against those 5 bad teams would be a better thing to list them by. If you don't win them while another team does then that's your own fault. Leafs would be still about middle of the pack showing they haven't had any great more opportunities that other teams have. Boston and Tampa would be near the top but not as much as they will be at the end of the year when the true advantage will be shown(when all the Atlantic teams will have the most games against other Atlantic teams).