History clearly shows the Disney plans were gathering dust long before the IOA design team came along.
I didn't read into these comments that people were claiming Disney actually stole from IOA, only that there are some interesting similarities between TDS and parts of IOA. I guess if the legand is true that former WDI staff borrowed concepts from BK to build Dueling Dragons, than it is possible they could have also borrowed on concepts they had seen (or maybe even worked on) from plans for the various incarnations of DisneySeas.
I assume that WDI departs have strong non-disclosure clauses they must sign. However, when it comes to recreating a mood, atmosphere, theme it would be hard not to draw on your past exposures and would seem easy to design something that while very similar, was not a legal transgression.