I believe it has to do with both the way the confirmation sentence is structured, and how the bank is named.
Naming the bank a your prefix may cause it to appear as if the sentence is mistyped.
IE naming it your savings will cause it to read as:
“YourYour Savingsaccount has been successfully attached!”
Currently, we can recommend not having a prefix of your when naming the bank.
But we do appreciate this feedback! I’ll make a note for our product team to see what the feasibility of cleaning up this sentence.