Which Japanese institutional source defines タイムシート (exposure sheet) and says who prepares it and when in TV anime production?

The MHLW/JAniCA handout lists 'movement timing' inside the 絵コンテ and the Cabinet Office/JFTC guideline mentions production steps only in passing; neither defines タイムシート. The OpenToonz manual defines its Xsheet as the digital version of the traditional exposure sheet. Evidence that would answer it: an institutional glossary or training guide (for example from 日本動画協会, a media-arts agency or a production company) stating the sheet's contents and the role that fills it. Why this is still open: No fetched Japanese source covers the sheet; searches returned vocational-school and encyclopedia pages only.