I noticed in here:
https://hub.spigotmc.org/stash/projects/SPIGOT/repos/craftbukkit/commits/3dda99c06f7fe23f5f9713dbd061b9598744e223#src%2Fmain%2Fjava%2Forg%2Fbukkit%2Fcraftbukkit%2FCraftServerTickManager.java?t=44

`Preconditions.checkArgument(tickRate > 1 && tickRate < 10_000, "The given tick rate must not be less than one");`

1) this should be either `> 0` or `>= 1` since 1 is acceptable
2) this should be either `< 10001` or `<= 10000` since 10000 is acceptable
3) The message should say "The given tick rate must be between 1 and 10,000"

This does throw an error when using 1 and 10,000, but I don't have code to provide as a test as it's part of my Skript addon Im working on.