It looks like, to avoid leaving behind TPi2.4 users, the firmware is still sticking to a 370 LEB budget and dedicating the additional 984(?) LEBs in TPi2.5 to the overlay, which at first made perfect sense to me but now I'm wondering how heavily people actually use their overlays. For reference, these are mine:

@ ssh black-bmc df -h /mnt/overlay
Filesystem                Size      Used Available Use% Mounted on
/dev/ubi0_2              24.0M      3.4M     20.6M  14% /mnt/overlay
@ ssh green-bmc df -h /mnt/overlay
Filesystem                Size      Used Available Use% Mounted on
/dev/ubi0_2              24.0M    812.0K     23.2M   3% /mnt/overlay