The Tile layout doesn't allow for variable row height, I think you need to use the ConstraintLayout. I have never used this, so that is all the help I can give.
In the documentation it says constraint layout is not supported for spart list.
Note: The Spark list-based controls (the Spark List control and its subclasses such as ButtonBar, ComboBox, DropDownList, and TabBar) do not support the ConstraintLayout class. Do not use ConstraintLayout with the Spark list-based controls.
TileLayout rows will take height of the row which has the biggest height value, if you want one of the cells to have a height which is less than that height, you can put your cell in a container, the container will take the height of the "highest" cell, while the content of your cell can now be adapted to your needs. I hope this helps.