Not only is there no "direct evidence" that the wife of Richard Johnson was Mary Taliaferro, a daughter of Robert Taliaferro, the immigrant, but all such evidence supports the theory that she was not.
First, during the 1680s a number of documents were recorded in Old Rappahannock and other counties that name some or all of the heirs of Robert Taliaferro, the immigrant. Not one names Richard Johnson or his wife. I would add that several name John Battaile, who married Robert Taliaferro's daughter Catherine. See for example, Rappahannock Co. Order Bk. 1685-87, p. 16; and esp. Stafford Co. Deeds & Wills, 1686-89, pp. 47-47a.
Second, Mr. Fritz states that the Taliaferros and Johnsons intermarried with the same families. Even if true, I don't see how this proves or suggests that they intermarried with each other. The children of Robert Taliaferro, the immigrant, intermarried with the families of Smith, Catlett, and Battaile. I know of no evidence that any Johnson intermarried with any of these families.
Third, Mr. Fritz sees the use of identical Christian names in the Taliaferro and Johnson families as "circumstantial evidence" for the marriage. The sons of Robert Taliaferro the immigrant were named Robert, Francis, John, Richard, and Charles. These names were in such common usage in 17th century Virginia that even if used by both families, they hardly provide evidence for anything.
I would point out the one established link between the Taliaferros and Johnsons. Charles Taliaferro, the youngest son of Robert the immigrant, was the neighbor of Richard Johnson.This fact alone is enough to explain the frequent appearance of his name on documents relating to the Johnson family.