That may be correct, it sounds compelling, but in the guide to healthcare practitioners it speaks of
in certain cases recommending a 'brief period of exemption' which means exemption can be for a finite period.
As far as I know from the people I have spoken to who are exempt, they do not told whether their exemption was open ended or finite
I would have thought it is unlawful if it is open ended and they send IB50 without further checking for exemption status by sending the GP an IB113 to be completed and considered by a ATOS doctor