Pokémon GO Wayfarer Challenge Rewards - Shiny Mankey (?)

- Pokémon GO: Fighting type Pokémon will appear more frequently in the wild and if you’re lucky you might encounter Shiny Mankey
Tier 1 vs Tier 2 rewards difference is "and if you’re lucky you might encounter Shiny Mankey".
What does this mean? Shiny Mankey was released in March 2019 in Battle Showdown event (https://pokemongolive.com/post/battleshowdown2019/?hl=en ) and it's available even today. Was the 'extra reward' for Tier 2 something like boosted shiny chances or just Mankey spawning at all?
Most of events introduces new shiny, this one is just a recycling of something that it's in game for almost two years already (and a lot players have it already) and I guess it wasn't compelling enough for PoGo players to even try to push to that Tier 2 rewards. Was this on purpose?
Comments
It's more likely similiar as boosted shiny Drifloon chance (in the wild) during Catch Mastery Challenge in Halloween 2020 event and any similiar events. If you're remember, shiny Drifloon was first released at Halloween 2018 event.
And iirc Niantic are just testing this event before they release similiar event like this in global scale.
Also, you might get more spawns, which boost your shiny chance aswell indirectly.