I kind of hate when people cherry-pick stats to be misleading, even if I otherwise support them.
The relevant number for NYC is not the percentage of hosts sharing a primary residence, but the percentage of total listings in NYC, or percentage of room-nights booked. I'm sure those numbers are far worse than 13%. Anyone renting non-primary residences is probably renting a lot of non-primary residences.
Also depends on how they classify 'NYC host'. Last month I rented a place on 1st Ave. that was actually owned by a real estate company in San Diego.
The place was fine, but the experience trying to coordinate with them was... not great. They were clearly just jumping on the bandwagon to make a quick buck.
You are correct that there are some hosts that list multiple properties, thus skewing the listing breakdown. It depends on the city. In most cities, room nights and revenue for "primary dwellings," meaning the homes people live in, are around 70-80%. We are in 34,000 cities, so this really varies quite widely. I would like to see the breakdown to be skewed much closer to primary dwellings for two reasons - (1) they have much higher review scores from guests, and (2) they don't typically enrich cities the way ordinary hosts do (though there are always exceptions. We are actually working with cities and our community to remove corporate rental companies that don't meet the above.
What is acceptable varies by market too (IMO). In Bali, the "owner lives in a house with 3-4 rental houses attached" is totally fine, and just as "authentic" as sharing a single house, since it's common for an extended family to live like that.
The relevant number for NYC is not the percentage of hosts sharing a primary residence, but the percentage of total listings in NYC, or percentage of room-nights booked. I'm sure those numbers are far worse than 13%. Anyone renting non-primary residences is probably renting a lot of non-primary residences.