There is a difference between nodal/leaf-bud/single-eye cuttings and 'leaf cuttings'.

Some leaf cuttings have preformed, primary meristems. We could simplify that statement by saying that these leaves have a group of cells that was engaged in meristematic (growth-extending) activity. These leaves come ready to rock with what is needed to form a shoot and grow.

Other leaf cuttings have tissues that are entirely differentiated. That is all the tissue is formed and dedicated to specific jobs other than acting as a growing point (meristem). These leaf cuttings produce secondary, wound-induced meristems. In these leaf cuttings, the dedicated tissues must first dedifferentiate and then change (redifferentiate) into new meristematic (growing) zones to form an adventitious bud.

In leaf cuttings, the ability to generate buds or shoots, not roots, is usually what determines success. Roots form much more readily than buds, and in some plants, rooted leaf cuttings can survive for years w/o producing an adventitious shoot. I witnessed this in a schefflera leaf I rooted years ago. I drilled a hole in a piece of lava, placed it in a tray of water, and inserted a schefflera leaf into the hole. After a few weeks it rooted, but I finally gave shoot growth up as a lost cause some 3 years into the adventure.

The short of it is, if you want to clone Ficus by way of cuttings, the propagules should have at least 2 nodes. I node is stripped of leaves and any growth in the leaf axil (on the part of the cutting that gets stuck (in the grow medium) and the other node (stays above the spoil line) can have a leaf or two and the leaves, if large) can be cut in cut in half across venation, or the node(s) can simply have a leaf scar.. It increases chances of rooting if the cutting is taken in late Jun or Jul (in the northern hemisphere), the parent plant is healthy, and the tools used are sterile and extremely sharp.

Rooted Ficus cutting ^^^ with new branches growing in leaf axils

Leaf/ bundle scar on Ficus ^^^ (just above the first branch), with suppressed buds above the scar.

Al

i am surprised you have any luck in what looks like wet sand ... aka dirt ...

but you do.. so who am i to say its not proper ...

the short story on Als discussion.. is that not all leaves will root or bud ...

do better research upfront ... including videos at a search engine relating to the plant you are trying to propagate ...

ken