You’re right, Stu. The wording of Regulation 10 of the former 1997 Crossings Regs regarding “Non-compliance with requirements … [that] is not such as materially to affect the general appearance of the crossing or the controlled area” is nowhere to be found in TSRGD 2016.
Nor is there the equivalent of paragraph 4 of Schedule 1 Part I of the 1997 Regs regarding the discolouration, disfigurement, imperfection or lack of illumination of zebra crossing globes or their posts, or to paragraph 12 of Part II, which says much the same for road markings at zebras.
The 1997 Regs are specifically called up for pelican crossings, so the above flexibility still applies to them, but not to other types of crossing.
During the Traffic Signs Policy Review that preceded the 2016 TSRGD various forms of wording of this nature were proposed to apply generally to all signs and markings, but these didn’t make it to the final cut.