had the same thing happen to me in sword, i was hunting galarian farfetch’d and got 2 swirlix instead lol

Had a similar thing happen to me in the exact same hunt! I think I went four or five phases for magmar here, one of which was only about 500 RE's too. That hunt was so crazy in general though because the first shiny koffing had a 5% smoke ball (which I actually sorely needed) and the total encounters for all the shinies combined was less than 8192. I lost my mind.

[gen4] OK THIS IS RIDICULOUS. Yesterday I entered phase 2 of Magmar with a shiny koffing, and now another one after only 502 REs!!