They don't put as much emphasis on employment for spousal sponsorship, you can sponsor and be unemployed. The reason they check up on visitor visa applicants is because that is used to determine if the applicant has ties to their home country. They take lying on visitor visa applications very seriously and those caught misrepresenting are hit with a 5 year ban.
They can't check a lot of what the applicant puts for occupation detail on the forms as I don't recall they even ask for phone numbers, but they could check up on the sponsor. However, do they require the sponsor to provide a letter from their employer, I'm assuming so they don't have to concern themselves as much about that detail.