just found that missing L/R balance figure in the new record (F/W 13.22) and all old records, I did wear running pod as usual.
Click on the little triangle ▼ to the right of the text "Ground Contact Time" above its graph. There's a drop down menu which selects between that and "Ground Contact Time Balance".
It's not related to the watch software but is a recent user interface change on the Garmin Connect website.