SIPPs and ISA transfers

Am I correct that when transferring shares from a SAYE scheme into an ISA or SIPP the tax treatment is slightly different? To an ISA is exempt from CGT, as long as transferred within 90 days of the scheme ending. To a SIPP is only exempt from CGT if transferred directly when the scheme ends. If done later than that, but within 90 days, there could be CGT if the value has increased between the day the shares are acquired, and the date they are transferred into the SIPP. Why is the treatment different?

Hi,
Please have a look at the guidance at Tax and Employee Share Schemes for the options available when transferring the shares.
Thank you.