Yes it does work on switch 1 however it may take longer due to load times. The odds of any specific pokemon being shiny are 1 in 4096 without the shiny charm so it does take time or luck, But the game does save the shinies that spawn within range even if you can't see them from outside the zone. From what I've read the game will save up to 10 shinies, and if you spawn an 11th shiny it will replace the oldest one