Hi Benjamin (& Kevin),
I know this is late, but you could also use text animators to adjust the scaling based on lines in order to keep everything on a single layer.
For full control, use a text animator for each line and separate them with range selectors, then adjust the scaling individually.
A quicker way is using a single text animator with randomized order and the shape you want (square won’t work unless you tweak the Start or End range), then use the random seed to adjust the result. Which might get a little fiddly, though.
Notice that you’ll need to set the text layer’s anchor point grouping to “Line” first and to add the line spacing property to the text animators to compensate for the misaligned leading due to the scaling.