Am I interpreting this relay pin diagram correctly?
Yes, you are right.

Anyway if you have doubts:


connect ohmmeter/continuity tester between 1 and 4 - if it shows zero resistance then this is the NC pin
do the same for pin 1 and 3. You should get open circuit.
between any coil pin and switch you should get open circuit.


I always do that, because I get confused with datasheets - top/bottom view.

Apply voltage to pin 2 and 5. Do the same test again. It should show opposite results.