Employers rely on healthcare providers’ expertise to determine how best to return an employee to work (or keep them at work) in part because employees aren’t qualified to diagnose the serious health conditions at issue. In the situation you describe, it makes sense to talk to the employee about the concerns they have about returning to work to determine if there is a compromise that can be struck that will help the employee to return. If the employee remains recalcitrant or resistant, explain to them that they will be held to the same policies (attendance, etc.) that others are held to.
Regarding inconsistent representations of the employee’s ability to work, courts place great weight on healthcare providers’ opinions. See Tonyan v. Dunham’s Athleisure Corp., 966 F.3d 681 (7th Cir. 2020), in which the court held that “the employer could rely on the employee’s doctor’s assessment of her capabilities when deciding whether she could perform the essential functions of her job.”