Huh, when I played 3.0 at MI Ranbats it was a vague blueish flash that was harder to spot. Haven't seen recent streams. Also, I brought up the point that your enemies would know as well when I asked for the change as well. In the end, I argue that, while the timer is certainly not something I think should affect Sonic for nearly as long as it does(this may change when 3.0 hits proper and I no longer have to deal with two separate timers), it is a buff to both sides - the player can more accurately react, and the opponent can, in turn, more accurately react to their reaction.
And then you can react to their reaction, which in turn they react to your reaction of their reaction to your ability to move, and then– well you get my point. In the end I find that Sonic has received two major buffs to Side-B in 3.0 - the singular reaction timer, and the fact he pops up a bit more when you use it in air and hold down the B Button, which works for recovery. The fact that the flash is a double-edged sword is a necessary change to help an opponent deal with a better version of an already good move.
It's amusing to see how much Sonic changes in as little as a week or a month. Having played a WIP Sonic at The Big House 3 and then again playing a more finalized 3.0 Sonic at MI Ranbats, and now I hear even more has changed, I have no idea what I'm getting in the hedgehog when Dec. 9th rolls around.