Steps to Reproduce:
1. Create a function tagged in "minecraft:tick".
2. Write in the created function:

execute as @a[tag=bug] run title @a title {"translate":"death.attack.generic","with":[{"selector":"@s"}]}

What I expected to happen was...:
For 1st selector: "(1) died"
For 2nd selector: "(2) died"

What actually happened was...:
For 1st selector: "(1) died"
For 2nd selector: "(1) died"

The video showing this:
https://youtu.be/4OqGOJprpGA

If you don't use the function tagged in "minecraft:tick", it will work fine:
https://youtu.be/YOSgsir7AJw