I can't find the event you are replying to, so I will answer in general.
No I did not think about that. If you enter the wrong password the decryption will fail, it won't give a decoy nsec.
nostr:nprofile1qqswuyd9ml6qcxd92h6pleptfrcqucvvjy39vg4wx7mv9wm8kakyujgpypmhxue69uhkx6r0wf6hxtndd94k2erfd3nk2u3wvdhk6w35xs6z7qgwwaehxw309ahx7uewd3hkctcpypmhxue69uhkummnw3ezuetfde6kuer6wasku7nfvuh8xurpvdjj7a0nq40 did you think about decoy nsecs in the NIP-49 spec using the wrong password?
I can't find the event you are replying to, so I will answer in general.
No I did not think about that. If you enter the wrong password the decryption will fail, it won't give a decoy nsec.