Yup. thats my reading of the law. I am no lawyer but it seems fairly clear to me.
6 Land over which access rights not exercisable
(1) The land in respect of which access rights are not exercisable is land—
(e) which has been developed or set out—
(i) as a sports or playing field; or
(ii) for a particular recreational purpose;
(2) Land which bears to be within section 6 above by virtue of a development or change of use for which planning permission was or is required under the Town and Country Planning (Scotland) Act 1997 (c. shall, if—
(a) such planning permission has not been granted; or
(b) such permission was granted subject to a condition which has not been complied with,
be regarded, for the purposes of that section, as if that development or change of use had not occurred.
So my reading is that planning permission has to be sought for land to be exempt from the provisions of the LRA under this section.
Edit - or a sherrif can declare it to be so but the assumption is full access unless specified other wise.
The other tack is that walkers would not be exercising their rights responsibly if they walk on the Fort William DH track for example.
Without test cases then a path remains a path IMO from my reading of the law unless planning has been sought for it to be exempt, This may be the case for the fort william DH track but it is not for the trail centres I don't believe and it willnot be for the DH track unless the planning has been sought.