Okay, I'll agree that it might not have a direct positive effect on the 'toll taking'-factors, but it might power it up. That's a plus in my eyes, but I can see the standpoint from the 'purist'-perspective.
Yeah, the BB Jolly Roger.. That's the one thing, but we still don't know the reason why he is able to go there. The one thing we know is exceptional about BB is his body, and that he is a D. This alone sets him apart from the vast majority for whom the 1DF-rule counts, as the D is still a rare trait. If the D allows for multiple DF's, then Oda wouldn't be backing down on any rule he specified, as it would still have meant that the vast majority of double fruit eaters would simply die, while the D's would just live on, but haven't ever tried to eat two: until BB.
We're in the NW now, the big difference so far is that DF's are going to become a bigger part of the storyline then ever before.
- Smile production
- Zoan armies
- Mera-mera no Mi becoming a critical plot point
- BB going around murdering DF users as if he's some Sylar rip off (Heroes).
Sure, DF's were present in the first part, and got slightly touched upon during CP9 (with the Giraffe and Bubble fruits), and the Marineford arc being the catalyst for BB, but the NW-arc is taking it far further then ever before.
My speculation is that if Oda wants to make an amendment to that rule he created more then 13 years ago, then he can at this point, if only for D's for example.