I got back to this subject after updating my lens firmware and deciding to turn IS off for what seemed a particularly good scene... It was a somewhat windy evening with the tripod firmly planted... on a grassy surface. It spoiled all subsequent shots. Luckily I got one* in before disabling IS, which kicked in because of the wind. Won't make that mistake again !As previously described, both Panasonic and Olympus bodies automatically disable all stabilisation when the amount of motion detected drops below a certain level. Even if you have IS switched on, it will turn itself off after the camera has been relatively static for about a second or so.
The only way to have IS active while the camera is on a tripod is to use an adapted, non-system, stabilised lens, such as an EF lens. This can be advantageous when shooting manual focus video with a long lens, because the OIS corrects the high-frequency bounce caused by touching the focus ring. Although the image will typically drift around a bit, the movement is relatively slow and is easy to correct in post, whereas the motion blur caused by unstabilised high-frequency lens bounce while shooting at around 1/50th second isn't. But in all other use cases, when using system lenses on a tripod, it makes no difference whether IS is turned on or off. It will always turn itself off.
LUMIX GX80 + PL 35-100 mm f/4.0-5.6 at 58mm - ƒ/5.6 - 1/3s - ISO 100
NB : Just heard Tony Northrup saying what you did on a recent video about common misconceptions in photography :