owever if the ILS glide path is available it is far better to stay on that glide slope until close to the flare
Fred. Agreed. Thanks for pointing that out. I should have amplified the expression `close to the flare`.
What I should have said was stay on the ILS glide slope within reasonable limits rather than completely disregard it. In another life with a government radio navigation aids testing unit, the ILS flight test required (among other things) flying the glide slope to below the standard Cat 1 DH to check for unusual indications of the type you mentioned. If something did not look right, technical investigation followed and if the problem could not be fixed, a note would be included on the relevant approach chart.