It could well be that the 7,500 figure mentioned by Chesky is the total of those directly employed by Airbnb, and the difference of 5,200 is made up of temps/contractors/agency staff. Cancel a contract with one call centre company and you could shed 1,000 jobs, which would not then be counted as “job losses”, simply the termination of a commercial agreement with company XYZ.
Alternatively, they could have been slightly over optimistic with employee numbers pre IPO, for whatever reason.
JF