Even though this is on April 1st I'd say this has about a 90% chance if not higher to be real. Apparently the person who shared this list leaks trophy lists early all the time and they're always legitimate.
The list may be incomplete though because SteamDB has a much larger list with a bunch of hidden trophies.
In terms of people saying this confirms no secret characters, one of the developers already confirmed in an interview I read a couple of months ago shortly after the reveal event that there are secret characters in the game. There's no way they'd put any information about secret characters in the trophy list, because that would make them no longer a secret lol.
MK games ALWAYS have very secretive things in them because Boon loves it that way. Whether this is the final trophy list or not, there will 100% be secret things in the game that aren't hinted at in any way in the final trophy list. At least 1 character for sure, possibly other finishers, hidden fights and maybe other stuff. You can bank on it, it's a series staple.
https://www.gamecrate.com/mortal-kombat-11-developer-interview-towers-of-time-how-gear-works-secret-characters/21980
GC: Are there any secret characters that you'll be able to unlock?
PG: There will be secret characters, sure.
About 3/4ths of the way through the interview, from Paulo himself.