If people prefer it this way, it doesn't need an argument. What reason is there to change it? In most scenarios where the hand is being shuffled, the opponent's likely to have seen most of them already.
Yes, there is a case where shuffling your hand would reveal information that your opponent didn't otherwise know, but the question then becomes whether the benefit of shuffling outweighs the drawback of showing your hand. Like any other card you take into your deck, you might just have to accept that it's not going to prove useful in every game.
If this is only being requested to benefit the use of
Whirlwind, then we're discussing changing game mechanics for the sake of a single card's balance issues. I don't want to see a situation where mass discard effects like Flare attack hide the results from the opponent because something else was changed.
If it is possible to change this ONLY for Whirlwind, then I have no objection, though I stand by my opinion that Whirlwind is balanced well at present and would need to be nerfed were this to change. (And personally, I like the drawback. It's more interesting.)