Why is it said that olive oil has a "body" (jirm) and is considered an insulator that prevents ablution, even though it does not form a layer on the skin, and experience shows that water penetrates through cloth covered with oil?

In Wudu' (ablution) and Ghusl (definition) (ritual bath), it is obligatory to remove anything that prevents water from reaching the skin, due to the Almighty's saying: "Wash your faces and your hands up to the elbows" (Al-Ma'idah/6). Anything that has a physical substance (jirm) and prevents water from reaching [the skin] must be removed, such as nail polish. However, if it has no physical substance, but only its color or oily residue remains, then it is not necessary to remove it, like olive oil and similar substances. Nevertheless, it is emphasized to rub the area with the hand to ensure that water reaches the entire limb.