From https://gerrit.libreoffice.org/c/core/+/168349 Write Help page accordingly.
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/4167f524c4718c3960cae2e4f390d04ffdb20839 tdf161442 Help page for Calc LET function