A new hire picks a health plan in Gusto, and if that plan runs through a carrier Gusto's brokerage already supports, the enrollment reaches the carrier on its own. If it doesn't, someone logs into that carrier's own site and re-enters the same employee, the same plan, the same effective date, by hand, and does it again for every change afterward.
The same gap shows up with 401(k) and other retirement providers. Gusto can sync payroll contributions to a supported provider automatically, but a provider outside that list needs eligibility and contribution data pulled together separately for census reporting, which usually means someone exporting payroll data and reformatting it into whatever file the provider wants.