I think you can use tags do differ them. In this scenario i think it's "d" tag. Ephemeral events also use specific tags for each app, but as a client you don't even have a way to prevent others apps to misbehave, like Vitor P. Issue of people sending DMs with kind 1. A client app cannot do nothing about it.
Discussion
Yes, people can simply use the wrong kind.
Probably really tempting because of the numbering. 1 is an easy, nice number. Otherwise, you have to go find the appropriate number and it won't be as nice. 981 or something.
Seems sort of silly, but there's a psychology to numbers. People will always start counting at the smallest number, so implementations will cluster most at the smallest numbers.
Same with the NIPs. They're in numerical order. Everyone reads NIP-01 and you've lost nearly everyone by NIP-25.
Only way to get people to pay attention to the kind and NIP content is to remove information from the numbers.