I wouldn't take the statement so literally as to mean "BioWare series have absolutely no influence on each other.", but rather to mean they're going to put the design goals of each franchise first and foremost when making the next game in that franchise, and then look to other games they and other studios make for additional influences and lessons to learn on what to and what not to do.
The WRPG genre in general consists of nigh 100% open worlds now, especially on the AAA scale. I don't think it's likely you will see another game without one any time soon.
Or, to make this more explicit, they're using the same technology as Dragon Age so it's safe to assume they have things like a similar character creator. They also are going to look at what people did and didn't like with Dragon Age's approach to open worlds to help inform what they do with their own open worlds instead of sticking their head in the sand and going "I CAN LEARN NOTHING FROM OTHER THINGS." like crazy people, especially given they share a lot of lower and mid level staff.
The people who make multiplayer for their games also share a lot of the same staff and very clearly take lessons from product to product.
However, similarly, they're not going to be Ubisoft and say "Every game must have capturable garrisons and parkour and stealth kills and 3000 collectibles because it got us to 10+ million sales in one game." They mentioned that Mass Effect won't have selectable races for example because they seem to feel that the series is about playing a human.