>>38939388It's the same 2-3% chance as any other legendary.
If you're consistently getting it, that means you're consistently getting a high number of premier balls because of high damage output, favourable team numbers, friendship bonuses, and favourable gym color.
Even with just 10 premier balls, if you practice the right throwing technique on what's one of the easier legendary targets, you'll be catching it 4 out of 5 times.
These chances jump to 19 out of 20 times if you get the maximum 18 premier balls.
