It would be helpful if we could see the exact wording of your question and the answer you got, just because there is some tricky stuff about smart locks.
In the older classic version of the smartthings mobile app, you could set up automations that would do pretty much anything you wanted to with a smart lock. You could unlock the lock based on geopresence, or via motion sensor or with a voice command. (I am myself am quadriparetic, so hands-free control of a lock is very important to me.)
However, the design philosophy for security features has changed with the newest version of the mobile app, the V3 version. Now the only way to unlock a smart lock is by opening the app and using the device icon. Or, of course, using the keypad on the lock itself.
But you can use the app from anywhere in the world as long as your phone has access to the Internet and the hub at your condo has access to the Internet.
In addition, the word “location“ has a very specific meaning on smartthings platform. You define different locations, and usually that’s associated with the hub. So if the hub is at home and you are 20 miles away at the office and you open the app you are still using the same “location“ as your hub at home. You obviously aren’t within Wi-Fi range, but from an account architecture standpoint, it’s all the same “location.“
Some people have one hub at home and one hub at the office And would therefore have two “locations.” You only have one app, but you have to switch within the app from one “location“ to the other and then you can only see the devices connected to that hub. So in that case you couldn’t be logged into the office location and control the lock at home. You would have to switch locations in the app first.
So that’s why the exact wording might make a difference. Especially if you had a first line support person who didn’t really know the answer themselves and was just looking it up in a database. It would be quite easy to find an answer that says “you cannot control devices from one location when you are signed into a different one.“
But to answer your general question, you can certainly be in New Jersey and use the new V3 app to unlock a lock at a condo in Miami, or use the official smart lock feature to change the lock codes on the lock in Miami. But you would have to be signed into the same “location“ as the hub which is controlling that lock.