@Lvrn 

When doing WPS the extender will copy both network names onto itself along with the wireless password to secure it.

If you look at the extender all three LED lights should be blue indicating it is configured.

What you can do then to change the wireless network names of the extender is to connect your smartphone to your wireless network, then open Tether. Tether should then find the RE450 and you will see it listed, tap on it to log into it and from there you can edit the extended network name.

Here is a FAQ that shows where to edit the network name: https://www.tp-link.com/us/support/faq/2540/

Having the same name may cause your devices confusion in that they may connect to your router when near the extender. It really is up to the device itself to determine where to connect to, but it is best to have the names different so you know exactly what network you are connecting to.