Joe, I respectfully disagree with your reasoning.
There is evidence that it was Rebecca Snow, daughter of William Snow and his wife, Rebecca Brown Snow, that married Samuel Rickard. If we also know that it was 2 sisters who married the Rickard brothers, it's only logical to assume that the "Mary" who is named in the Plymouth documents as mother of John Rickard's children, was Mary Snow, sister of Rebecca Snow. Mary is also named first in her father, William Snow's Will. She definitely existed.
There are many cases in 17th Century colonial America where documents and even whole civil registers were lost or destroyed, yet the relationships, based on evidence similar to that in this case, remain posted on WikiTree. I believe this should be one of those cases and I will always oppose detaching Mary, sister of Rebecca Snow Rickard, from either her Snow parents or the husband and father of her children, John Rickard. With Ellen Smith's additional comments on the profiles involved, I think that the standard of "a reasonable discussion of the evidence" is met and anyone reading these profiles can see that there are pros and cons to the subject.