I can think of a few reasons Elon wouldn't want to reveal that Rajnesh Pundabaaba was running his account (if that's what happened - it could've been 100% him).

One, he's been investigated for financial crimes for "inappropriately" influencing the stock market with his tweets. Maybe the fact that someone else covers for him on X would help his legal protection there, or it could throw a monkey wrench into it.

Two, he loses a lot of the power of X when people assume that an H-1B is tweeting instead of the richest man in the world.

Three, and maybe most importantly, he loses a lot of the Most Interesting Nerd in the World cachet. This is a guy who won't cop to hiring a smurf in PoE and beefs with reaction streamers. If people like Joe Rogan realize he falls a little short of a 13-year old's fever dream of a hero that can design rockets with one hand and world rank in video games with the other while posting dank memes 24/7, that would immensely hurt him.

Now you might say that burning bridges with the online right isn't worth those things, and maybe that's correct, but I could see the cost benefit working out the other way in his mind.