when did Airbnb Plus program start to include exclusivity as one of the requirements to become Plus?

[JooHo0]

when did Airbnb Plus program start to include exclusivity(take off listings from other websites) as one of the requirements to become Plus?

I've read some conversations in the community and people were not quite satisfied with this exclusivity requirement. 

When Plus program was launched in early 2018, Airbnb did not have the exclusivity requirement to become Plus, as I remember (at least until early 2019).

Could someone (e.g. hosts whose listings became Plus in 2018) let me know when this became a requirement?