Acacia saplings can grow without a block of dirt under them and actually generate a block of dirt when grown

When using the /setblock command to place an acacia sapling in midair, it will grow, and once it has grown, it will generate a dirt block underneath. I have only tested it on 1.21 and 1.21.1 but it may also work on other versions like 1.18 or 1.21.4