Sorry but that's rubbish. Standard PCG advice is to keep membership for the year after you finish contracting, and has been for many years. IR35 inquiries are based on your SAR, which is submitted in the tax year after the one it refers to, hence one extra year to be safe. Or, if you're closing your company, to cover you in case HMRC find something in the closing process and raise an inquiry on that.
And it's IPSE these days.