You won't get two fields to link simply by naming them the same thing, because underneath they are actually two different fields with different parents. If you show the SOM value of both fields, you will see that they are different. [1]
The best way to do this would be create a rule on the 1st field that updates the 2nd field when it detects a change. If you want it to work the other way as well, then create a rule on the 2nd field that changes the 1st field when it detects the value has changed. This would be an explicit link where it was obvious to another developer that the two fields are linked.
Another way to do this would be to bind the fields to the same entry in the form schema. This will automatically update the values as they change. This is more of an implicit binding of the two fields.
I would avoid naming your fields the same thing as a general rule as unpredictable results might occur.
[1] Adobe Experience Manager Help | Using SOM expressions in adaptive forms