This question concerns part of the complex sugya of 95b. The Gemoro says that if Reuven's brother-in-law (Moshe) went away to Medinas HaYam (with Reuven's wife), and Reuven married Moshe's wife (Rochel, his wife's sister) - on Moshe's return Reuven must give Rochel a Get, but she is not permitted to return to Moshe.
Reb Yitzchok Nafcha explains that when Reuven gives Rochel a Get, people may think that Moshe also had given Rochel a Get before he went away, which would mean that if Rochel were allowed to return to Moshe - it looks like Machzir Gerushoso.
The question is: if people see Reuven give Rochel a Get - doesn't that imply that Moshe had NOT given Rochel a Get?! (If Moshe had given a Get - Reuven would be legally married to Rochel, and would not HAVE to give a Get!)
[The only answer I could think of is that people may not know that
Reuven is giving a Get on instruction of Beis Din due to the
return of Moshe, but may think he is Stam giving a Get]
Your answer is right on the mark, Mark. It is generally assumed that when people see a Get that they will take for granted that the couple were married.